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	$147.77	5.779%	$156.3096	$156.31	$156.30	$156.30
Purchase #2	$79.72	10.232%	$87.877	$87.88	$87.90	$87.90
Purchase #3	$100.93	10.591%	$111.6195	$111.62	$111.60	$111.60
Purchase #4	$90.77	4.559%	$94.9082	$94.91	$94.90	$94.90
Purchase #5	$71.57	13.382%	$81.1475	$81.15	$81.15	$81.10
Purchase #6	$160.70	12.560%	$180.8839	$180.88	$180.90	$180.90
Purchase #7	$13.94	12.423%	$15.6718	$15.67	$15.65	$15.70
7 purchase totals =	$665.40		$728.4175	$728.42	$728.40	$728.40