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	$161.32	6.199%	$171.3202	$171.32	$171.30	$171.30
Purchase #2	$56.76	9.769%	$62.3049	$62.30	$62.30	$62.30
Purchase #3	$236.68	11.268%	$263.3491	$263.35	$263.35	$263.30
Purchase #4	$224.82	4.729%	$235.4517	$235.45	$235.45	$235.50
Purchase #5	$38.25	12.303%	$42.9559	$42.96	$42.95	$43.00
Purchase #6	$165.51	9.281%	$180.871	$180.87	$180.85	$180.90
Purchase #7	$75.68	3.123%	$78.0435	$78.04	$78.05	$78.00
7 purchase totals =	$959.02		$1,034.2963	$1,034.29	$1,034.25	$1,034.30