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	$248.76	6.765%	$265.5886	$265.59	$265.60	$265.60
Purchase #2	$210.42	11.170%	$233.9239	$233.92	$233.90	$233.90
Purchase #3	$102.97	6.263%	$109.419	$109.42	$109.40	$109.40
Purchase #4	$105.94	6.701%	$113.039	$113.04	$113.05	$113.00
Purchase #5	$209.72	13.821%	$238.7054	$238.71	$238.70	$238.70
Purchase #6	$195.44	10.814%	$216.5749	$216.57	$216.55	$216.60
Purchase #7	$164.73	4.459%	$172.0753	$172.08	$172.10	$172.10
7 purchase totals =	$1,237.98		$1,349.3261	$1,349.33	$1,349.30	$1,349.30