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	$225.49	8.747%	$245.2136	$245.21	$245.20	$245.20
Purchase #2	$160.53	4.540%	$167.8181	$167.82	$167.80	$167.80
Purchase #3	$67.73	6.513%	$72.1413	$72.14	$72.15	$72.10
Purchase #4	$90.68	9.559%	$99.3481	$99.35	$99.35	$99.30
Purchase #5	$43.81	5.429%	$46.1884	$46.19	$46.20	$46.20
Purchase #6	$234.27	6.471%	$249.4296	$249.43	$249.45	$249.40
Purchase #7	$157.45	5.614%	$166.2892	$166.29	$166.30	$166.30
7 purchase totals =	$979.96		$1,046.4283	$1,046.43	$1,046.45	$1,046.30