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	$213.93	13.363%	$242.5175	$242.52	$242.50	$242.50
Purchase #2	$28.77	8.158%	$31.1171	$31.12	$31.10	$31.10
Purchase #3	$244.50	13.491%	$277.4855	$277.49	$277.50	$277.50
Purchase #4	$67.77	5.229%	$71.3137	$71.31	$71.30	$71.30
Purchase #5	$61.34	4.779%	$64.2714	$64.27	$64.25	$64.30
Purchase #6	$221.93	8.391%	$240.5521	$240.55	$240.55	$240.60
Purchase #7	$60.59	7.370%	$65.0555	$65.06	$65.05	$65.10
7 purchase totals =	$898.83		$992.3128	$992.32	$992.25	$992.40