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	$202.74	10.568%	$224.1656	$224.17	$224.15	$224.20
Purchase #2	$150.30	10.281%	$165.7523	$165.75	$165.75	$165.80
Purchase #3	$209.41	6.688%	$223.4153	$223.42	$223.40	$223.40
Purchase #4	$18.48	13.128%	$20.9061	$20.91	$20.90	$20.90
Purchase #5	$32.69	8.273%	$35.3944	$35.39	$35.40	$35.40
Purchase #6	$47.43	4.372%	$49.5036	$49.50	$49.50	$49.50
Purchase #7	$39.47	3.319%	$40.78	$40.78	$40.80	$40.80
7 purchase totals =	$700.52		$759.9173	$759.92	$759.90	$760.00