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	$19.81	13.499%	$22.4842	$22.48	$22.50	$22.50
Purchase #2	$196.76	13.449%	$223.2223	$223.22	$223.20	$223.20
Purchase #3	$229.43	3.561%	$237.6	$237.60	$237.60	$237.60
Purchase #4	$95.89	4.776%	$100.4697	$100.47	$100.45	$100.50
Purchase #5	$172.38	9.710%	$189.1181	$189.12	$189.10	$189.10
Purchase #6	$174.76	9.489%	$191.343	$191.34	$191.35	$191.30
Purchase #7	$92.98	4.436%	$97.1046	$97.10	$97.10	$97.10
7 purchase totals =	$982.01		$1,061.3419	$1,061.33	$1,061.30	$1,061.30