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	$180.60	3.372%	$186.6898	$186.69	$186.70	$186.70
Purchase #2	$148.61	11.169%	$165.2083	$165.21	$165.20	$165.20
Purchase #3	$136.27	7.612%	$146.6429	$146.64	$146.65	$146.60
Purchase #4	$67.36	6.281%	$71.5909	$71.59	$71.60	$71.60
Purchase #5	$92.71	8.769%	$100.8397	$100.84	$100.85	$100.80
Purchase #6	$215.40	7.533%	$231.6261	$231.63	$231.65	$231.60
Purchase #7	$170.75	8.247%	$184.8318	$184.83	$184.85	$184.80
7 purchase totals =	$1,011.70		$1,087.4295	$1,087.43	$1,087.50	$1,087.30