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	$40.31	13.846%	$45.8913	$45.89	$45.90	$45.90
Purchase #2	$218.74	11.667%	$244.2604	$244.26	$244.25	$244.30
Purchase #3	$181.58	11.852%	$203.1009	$203.10	$203.10	$203.10
Purchase #4	$89.25	13.560%	$101.3523	$101.35	$101.35	$101.40
Purchase #5	$72.82	9.700%	$79.8835	$79.88	$79.90	$79.90
Purchase #6	$52.38	4.321%	$54.6433	$54.64	$54.65	$54.60
Purchase #7	$200.39	9.668%	$219.7637	$219.76	$219.75	$219.80
7 purchase totals =	$855.47		$948.8954	$948.88	$948.90	$949.00