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	$168.62	11.549%	$188.0939	$188.09	$188.10	$188.10
Purchase #2	$18.92	12.686%	$21.3202	$21.32	$21.30	$21.30
Purchase #3	$65.48	5.537%	$69.1056	$69.11	$69.10	$69.10
Purchase #4	$203.99	3.735%	$211.609	$211.61	$211.60	$211.60
Purchase #5	$43.56	11.359%	$48.508	$48.51	$48.50	$48.50
Purchase #6	$32.39	3.387%	$33.487	$33.49	$33.50	$33.50
Purchase #7	$55.26	7.688%	$59.5084	$59.51	$59.50	$59.50
7 purchase totals =	$588.22		$631.6321	$631.64	$631.60	$631.60