Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$164.75	8.513%	$178.7752	$178.78	$178.80	$178.80
Purchase #2	$165.65	10.121%	$182.4154	$182.42	$182.40	$182.40
Purchase #3	$183.43	7.334%	$196.8828	$196.88	$196.90	$196.90
Purchase #4	$219.66	10.364%	$242.4256	$242.43	$242.45	$242.40
Purchase #5	$91.36	11.669%	$102.0208	$102.02	$102.00	$102.00
Purchase #6	$163.46	5.425%	$172.3277	$172.33	$172.35	$172.30
Purchase #7	$100.67	13.573%	$114.3339	$114.33	$114.35	$114.30
7 purchase totals =	$1,088.98		$1,189.1814	$1,189.19	$1,189.25	$1,189.10