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	$72.41	8.406%	$78.4968	$78.50	$78.50	$78.50
Purchase #2	$20.44	4.368%	$21.3328	$21.33	$21.35	$21.30
Purchase #3	$46.57	4.668%	$48.7439	$48.74	$48.75	$48.70
Purchase #4	$89.85	10.162%	$98.9806	$98.98	$99.00	$99.00
Purchase #5	$106.91	3.199%	$110.3301	$110.33	$110.35	$110.30
Purchase #6	$41.57	8.479%	$45.0947	$45.09	$45.10	$45.10
Purchase #7	$189.47	3.248%	$195.624	$195.62	$195.60	$195.60
7 purchase totals =	$567.22		$598.6029	$598.59	$598.65	$598.50