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	$97.41	5.763%	$103.0237	$103.02	$103.00	$103.00
Purchase #2	$94.94	4.539%	$99.2493	$99.25	$99.25	$99.20
Purchase #3	$68.90	10.144%	$75.8892	$75.89	$75.90	$75.90
Purchase #4	$78.75	13.341%	$89.256	$89.26	$89.25	$89.30
Purchase #5	$139.33	10.841%	$154.4348	$154.43	$154.45	$154.40
Purchase #6	$50.70	9.373%	$55.4521	$55.45	$55.45	$55.50
Purchase #7	$172.50	6.860%	$184.3335	$184.33	$184.35	$184.30
7 purchase totals =	$702.53		$761.6386	$761.63	$761.65	$761.60