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	$162.39	5.129%	$170.719	$170.72	$170.70	$170.70
Purchase #2	$185.30	13.841%	$210.9474	$210.95	$210.95	$210.90
Purchase #3	$79.35	12.229%	$89.0537	$89.05	$89.05	$89.10
Purchase #4	$91.82	9.643%	$100.6742	$100.67	$100.65	$100.70
Purchase #5	$119.97	11.796%	$134.1217	$134.12	$134.10	$134.10
Purchase #6	$125.59	8.637%	$136.4372	$136.44	$136.45	$136.40
Purchase #7	$211.87	4.849%	$222.1436	$222.14	$222.15	$222.10
7 purchase totals =	$976.29		$1,064.0968	$1,064.09	$1,064.05	$1,064.00