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	$139.87	10.558%	$154.6375	$154.64	$154.65	$154.60
Purchase #2	$85.41	4.377%	$89.1484	$89.15	$89.15	$89.10
Purchase #3	$248.48	3.399%	$256.9258	$256.93	$256.95	$256.90
Purchase #4	$157.61	4.698%	$165.0145	$165.01	$165.00	$165.00
Purchase #5	$133.77	12.108%	$149.9669	$149.97	$149.95	$150.00
Purchase #6	$224.86	5.505%	$237.2385	$237.24	$237.25	$237.20
Purchase #7	$70.39	11.283%	$78.3321	$78.33	$78.35	$78.30
7 purchase totals =	$1,060.39		$1,131.2637	$1,131.27	$1,131.30	$1,131.10