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	$233.32	9.339%	$255.1098	$255.11	$255.10	$255.10
Purchase #2	$91.39	9.756%	$100.306	$100.31	$100.30	$100.30
Purchase #3	$122.57	12.837%	$138.3043	$138.30	$138.30	$138.30
Purchase #4	$144.52	7.208%	$154.937	$154.94	$154.95	$154.90
Purchase #5	$27.72	12.354%	$31.1445	$31.14	$31.15	$31.10
Purchase #6	$151.92	12.740%	$171.2746	$171.27	$171.25	$171.30
Purchase #7	$205.86	7.805%	$221.9274	$221.93	$221.95	$221.90
7 purchase totals =	$977.30		$1,073.0036	$1,073.00	$1,073.00	$1,072.90