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	$56.64	10.807%	$62.7611	$62.76	$62.75	$62.80
Purchase #2	$83.32	11.260%	$92.7018	$92.70	$92.70	$92.70
Purchase #3	$134.61	7.360%	$144.5173	$144.52	$144.50	$144.50
Purchase #4	$66.25	11.516%	$73.8794	$73.88	$73.90	$73.90
Purchase #5	$77.41	8.319%	$83.8497	$83.85	$83.85	$83.80
Purchase #6	$52.59	8.281%	$56.945	$56.95	$56.95	$56.90
Purchase #7	$129.91	12.111%	$145.6434	$145.64	$145.65	$145.60
7 purchase totals =	$600.73		$660.2977	$660.30	$660.30	$660.20