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	$59.27	8.151%	$64.1011	$64.10	$64.10	$64.10
Purchase #2	$170.44	4.521%	$178.1456	$178.15	$178.15	$178.10
Purchase #3	$63.72	12.146%	$71.4594	$71.46	$71.45	$71.50
Purchase #4	$236.59	11.256%	$263.2206	$263.22	$263.20	$263.20
Purchase #5	$168.77	12.799%	$190.3709	$190.37	$190.35	$190.40
Purchase #6	$180.36	5.314%	$189.9443	$189.94	$189.95	$189.90
Purchase #7	$173.32	12.197%	$194.4598	$194.46	$194.45	$194.50
7 purchase totals =	$1,052.47		$1,151.7017	$1,151.70	$1,151.65	$1,151.70