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	$197.26	12.708%	$222.3278	$222.33	$222.35	$222.30
Purchase #2	$57.57	6.114%	$61.0898	$61.09	$61.10	$61.10
Purchase #3	$202.77	4.270%	$211.4283	$211.43	$211.45	$211.40
Purchase #4	$64.77	13.429%	$73.468	$73.47	$73.45	$73.50
Purchase #5	$171.59	7.416%	$184.3151	$184.32	$184.30	$184.30
Purchase #6	$86.29	6.800%	$92.1577	$92.16	$92.15	$92.20
Purchase #7	$220.91	8.607%	$239.9237	$239.92	$239.90	$239.90
7 purchase totals =	$1,001.16		$1,084.7104	$1,084.72	$1,084.70	$1,084.70