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	$145.38	3.443%	$150.3854	$150.39	$150.40	$150.40
Purchase #2	$146.74	12.826%	$165.5609	$165.56	$165.55	$165.60
Purchase #3	$73.41	7.564%	$78.9627	$78.96	$78.95	$79.00
Purchase #4	$182.94	5.350%	$192.7273	$192.73	$192.75	$192.70
Purchase #5	$153.71	8.357%	$166.5555	$166.56	$166.55	$166.60
Purchase #6	$62.95	13.375%	$71.3696	$71.37	$71.35	$71.40
Purchase #7	$247.75	6.434%	$263.6902	$263.69	$263.70	$263.70
7 purchase totals =	$1,012.88		$1,089.2516	$1,089.26	$1,089.25	$1,089.40