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	$46.31	13.803%	$52.7022	$52.70	$52.70	$52.70
Purchase #2	$51.25	11.138%	$56.9582	$56.96	$56.95	$57.00
Purchase #3	$10.39	5.524%	$10.9639	$10.96	$10.95	$11.00
Purchase #4	$96.36	4.104%	$100.3146	$100.31	$100.30	$100.30
Purchase #5	$24.46	13.644%	$27.7973	$27.80	$27.80	$27.80
Purchase #6	$140.58	13.587%	$159.6806	$159.68	$159.70	$159.70
Purchase #7	$33.86	10.685%	$37.4779	$37.48	$37.50	$37.50
7 purchase totals =	$403.21		$445.8947	$445.89	$445.90	$446.00