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	$40.44	13.306%	$45.8209	$45.82	$45.80	$45.80
Purchase #2	$78.64	4.416%	$82.1127	$82.11	$82.10	$82.10
Purchase #3	$91.63	5.744%	$96.8932	$96.89	$96.90	$96.90
Purchase #4	$56.56	9.342%	$61.8438	$61.84	$61.85	$61.80
Purchase #5	$169.84	8.646%	$184.5244	$184.52	$184.50	$184.50
Purchase #6	$200.40	11.353%	$223.1514	$223.15	$223.15	$223.20
Purchase #7	$221.56	10.128%	$243.9996	$244.00	$244.00	$244.00
7 purchase totals =	$859.07		$938.3460	$938.33	$938.30	$938.30