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	$186.41	5.300%	$196.2897	$196.29	$196.30	$196.30
Purchase #2	$191.68	9.408%	$209.7133	$209.71	$209.70	$209.70
Purchase #3	$159.76	11.578%	$178.257	$178.26	$178.25	$178.30
Purchase #4	$127.65	10.471%	$141.0162	$141.02	$141.00	$141.00
Purchase #5	$199.30	3.524%	$206.3233	$206.32	$206.30	$206.30
Purchase #6	$165.42	7.688%	$178.1375	$178.14	$178.15	$178.10
Purchase #7	$46.95	12.527%	$52.8314	$52.83	$52.85	$52.80
7 purchase totals =	$1,077.17		$1,162.5684	$1,162.57	$1,162.55	$1,162.50