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	$134.59	13.483%	$152.7368	$152.74	$152.75	$152.70
Purchase #2	$178.80	11.687%	$199.6964	$199.70	$199.70	$199.70
Purchase #3	$229.46	10.324%	$253.1495	$253.15	$253.15	$253.10
Purchase #4	$158.79	10.170%	$174.9389	$174.94	$174.95	$174.90
Purchase #5	$31.87	9.479%	$34.891	$34.89	$34.90	$34.90
Purchase #6	$84.53	7.820%	$91.1402	$91.14	$91.15	$91.10
Purchase #7	$124.86	13.178%	$141.3141	$141.31	$141.30	$141.30
7 purchase totals =	$942.90		$1,047.8669	$1,047.87	$1,047.90	$1,047.70