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	$53.94	10.118%	$59.3976	$59.40	$59.40	$59.40
Purchase #2	$119.63	4.152%	$124.597	$124.60	$124.60	$124.60
Purchase #3	$36.87	10.122%	$40.602	$40.60	$40.60	$40.60
Purchase #4	$169.44	3.234%	$174.9197	$174.92	$174.90	$174.90
Purchase #5	$177.50	4.738%	$185.91	$185.91	$185.90	$185.90
Purchase #6	$28.51	6.753%	$30.4353	$30.44	$30.45	$30.40
Purchase #7	$173.57	3.466%	$179.5859	$179.59	$179.60	$179.60
7 purchase totals =	$759.46		$795.4475	$795.46	$795.45	$795.40