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	$65.98	9.499%	$72.2474	$72.25	$72.25	$72.20
Purchase #2	$116.30	9.293%	$127.1078	$127.11	$127.10	$127.10
Purchase #3	$200.36	5.794%	$211.9689	$211.97	$211.95	$212.00
Purchase #4	$54.34	8.624%	$59.0263	$59.03	$59.05	$59.00
Purchase #5	$38.62	7.749%	$41.6127	$41.61	$41.60	$41.60
Purchase #6	$147.52	12.790%	$166.3878	$166.39	$166.40	$166.40
Purchase #7	$165.34	9.552%	$181.1333	$181.13	$181.15	$181.10
7 purchase totals =	$788.46		$859.4842	$859.49	$859.50	$859.40