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	$149.83	12.627%	$168.749	$168.75	$168.75	$168.70
Purchase #2	$155.90	6.314%	$165.7435	$165.74	$165.75	$165.70
Purchase #3	$250.46	11.345%	$278.8747	$278.87	$278.85	$278.90
Purchase #4	$8.47	4.748%	$8.8722	$8.87	$8.85	$8.90
Purchase #5	$153.34	11.661%	$171.221	$171.22	$171.20	$171.20
Purchase #6	$85.43	3.118%	$88.0937	$88.09	$88.10	$88.10
Purchase #7	$162.34	4.350%	$169.4018	$169.40	$169.40	$169.40
7 purchase totals =	$965.77		$1,050.9559	$1,050.94	$1,050.90	$1,050.90