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	$33.83	5.713%	$35.7627	$35.76	$35.75	$35.80
Purchase #2	$149.34	10.623%	$165.2044	$165.20	$165.20	$165.20
Purchase #3	$232.61	10.256%	$256.4665	$256.47	$256.45	$256.50
Purchase #4	$75.82	8.744%	$82.4497	$82.45	$82.45	$82.40
Purchase #5	$234.38	11.474%	$261.2728	$261.27	$261.25	$261.30
Purchase #6	$26.56	4.292%	$27.7	$27.70	$27.70	$27.70
Purchase #7	$214.71	10.218%	$236.6491	$236.65	$236.65	$236.60
7 purchase totals =	$967.25		$1,065.5052	$1,065.50	$1,065.45	$1,065.50