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	$89.96	6.454%	$95.766	$95.77	$95.75	$95.80
Purchase #2	$66.35	7.134%	$71.0834	$71.08	$71.10	$71.10
Purchase #3	$105.52	13.707%	$119.9836	$119.98	$120.00	$120.00
Purchase #4	$155.29	7.629%	$167.1371	$167.14	$167.15	$167.10
Purchase #5	$110.92	11.508%	$123.6847	$123.68	$123.70	$123.70
Purchase #6	$160.59	6.777%	$171.4732	$171.47	$171.45	$171.50
Purchase #7	$91.69	8.330%	$99.3278	$99.33	$99.35	$99.30
7 purchase totals =	$780.32		$848.4558	$848.45	$848.50	$848.50