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	$173.29	7.150%	$185.6802	$185.68	$185.70	$185.70
Purchase #2	$118.51	10.867%	$131.3885	$131.39	$131.40	$131.40
Purchase #3	$28.65	7.858%	$30.9013	$30.90	$30.90	$30.90
Purchase #4	$216.51	12.276%	$243.0888	$243.09	$243.10	$243.10
Purchase #5	$247.33	3.736%	$256.5702	$256.57	$256.55	$256.60
Purchase #6	$81.75	9.769%	$89.7362	$89.74	$89.75	$89.70
Purchase #7	$88.77	3.379%	$91.7695	$91.77	$91.75	$91.80
7 purchase totals =	$954.81		$1,029.1347	$1,029.14	$1,029.15	$1,029.20