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	$196.99	6.569%	$209.9303	$209.93	$209.95	$209.90
Purchase #2	$100.55	11.227%	$111.8387	$111.84	$111.85	$111.80
Purchase #3	$99.38	3.378%	$102.7371	$102.74	$102.75	$102.70
Purchase #4	$69.43	3.630%	$71.9503	$71.95	$71.95	$72.00
Purchase #5	$182.30	9.257%	$199.1755	$199.18	$199.20	$199.20
Purchase #6	$219.90	10.671%	$243.3655	$243.37	$243.35	$243.40
Purchase #7	$136.38	5.667%	$144.1087	$144.11	$144.10	$144.10
7 purchase totals =	$1,004.93		$1,083.1061	$1,083.12	$1,083.15	$1,083.10