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	$228.70	11.418%	$254.813	$254.81	$254.80	$254.80
Purchase #2	$160.71	8.325%	$174.0891	$174.09	$174.10	$174.10
Purchase #3	$152.89	9.340%	$167.1699	$167.17	$167.15	$167.20
Purchase #4	$41.68	8.717%	$45.3132	$45.31	$45.30	$45.30
Purchase #5	$112.27	12.658%	$126.4811	$126.48	$126.50	$126.50
Purchase #6	$179.28	3.649%	$185.8219	$185.82	$185.80	$185.80
Purchase #7	$187.94	13.388%	$213.1014	$213.10	$213.10	$213.10
7 purchase totals =	$1,063.47		$1,166.7896	$1,166.78	$1,166.75	$1,166.80