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	$185.59	13.646%	$210.9156	$210.92	$210.90	$210.90
Purchase #2	$46.85	12.852%	$52.8712	$52.87	$52.85	$52.90
Purchase #3	$56.89	5.755%	$60.164	$60.16	$60.15	$60.20
Purchase #4	$124.91	13.818%	$142.1701	$142.17	$142.15	$142.20
Purchase #5	$87.30	7.481%	$93.8309	$93.83	$93.85	$93.80
Purchase #6	$104.76	6.625%	$111.7004	$111.70	$111.70	$111.70
Purchase #7	$226.36	8.629%	$245.8926	$245.89	$245.90	$245.90
7 purchase totals =	$832.66		$917.5448	$917.54	$917.50	$917.60