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	$218.39	9.307%	$238.7156	$238.72	$238.70	$238.70
Purchase #2	$152.62	4.501%	$159.4894	$159.49	$159.50	$159.50
Purchase #3	$229.84	4.252%	$239.6128	$239.61	$239.60	$239.60
Purchase #4	$32.83	9.361%	$35.9032	$35.90	$35.90	$35.90
Purchase #5	$233.48	4.804%	$244.6964	$244.70	$244.70	$244.70
Purchase #6	$61.70	9.289%	$67.4313	$67.43	$67.45	$67.40
Purchase #7	$114.42	4.742%	$119.8458	$119.85	$119.85	$119.80
7 purchase totals =	$1,043.28		$1,105.6945	$1,105.70	$1,105.70	$1,105.60