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	$33.72	5.404%	$35.5422	$35.54	$35.55	$35.50
Purchase #2	$176.81	10.801%	$195.9072	$195.91	$195.90	$195.90
Purchase #3	$64.29	4.227%	$67.0075	$67.01	$67.00	$67.00
Purchase #4	$111.85	5.225%	$117.6942	$117.69	$117.70	$117.70
Purchase #5	$165.78	5.680%	$175.1963	$175.20	$175.20	$175.20
Purchase #6	$53.27	3.675%	$55.2277	$55.23	$55.25	$55.20
Purchase #7	$239.81	4.581%	$250.7957	$250.80	$250.80	$250.80
7 purchase totals =	$845.53		$897.3708	$897.38	$897.40	$897.30