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	$39.91	13.836%	$45.4319	$45.43	$45.45	$45.40
Purchase #2	$103.35	5.264%	$108.7903	$108.79	$108.80	$108.80
Purchase #3	$213.78	12.343%	$240.1669	$240.17	$240.15	$240.20
Purchase #4	$33.52	11.112%	$37.2447	$37.24	$37.25	$37.20
Purchase #5	$40.98	13.585%	$46.5471	$46.55	$46.55	$46.50
Purchase #6	$227.40	11.379%	$253.2758	$253.28	$253.30	$253.30
Purchase #7	$144.61	3.863%	$150.1963	$150.20	$150.20	$150.20
7 purchase totals =	$803.55		$881.6530	$881.66	$881.70	$881.60