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	$143.97	8.112%	$155.6488	$155.65	$155.65	$155.60
Purchase #2	$97.38	9.606%	$106.7343	$106.73	$106.75	$106.70
Purchase #3	$93.63	12.612%	$105.4386	$105.44	$105.45	$105.40
Purchase #4	$241.33	11.735%	$269.6501	$269.65	$269.65	$269.70
Purchase #5	$237.97	5.157%	$250.2421	$250.24	$250.25	$250.20
Purchase #6	$89.34	12.662%	$100.6522	$100.65	$100.65	$100.70
Purchase #7	$41.54	10.529%	$45.9137	$45.91	$45.90	$45.90
7 purchase totals =	$945.16		$1,034.2798	$1,034.27	$1,034.30	$1,034.20