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	$140.71	12.519%	$158.3255	$158.33	$158.35	$158.30
Purchase #2	$244.50	7.626%	$263.1456	$263.15	$263.15	$263.10
Purchase #3	$33.93	12.793%	$38.2707	$38.27	$38.25	$38.30
Purchase #4	$160.69	11.479%	$179.1356	$179.14	$179.15	$179.10
Purchase #5	$148.70	6.325%	$158.1053	$158.11	$158.10	$158.10
Purchase #6	$100.38	12.378%	$112.805	$112.81	$112.80	$112.80
Purchase #7	$185.95	5.568%	$196.3037	$196.30	$196.30	$196.30
7 purchase totals =	$1,014.86		$1,106.0914	$1,106.11	$1,106.10	$1,106.00