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	$118.26	7.846%	$127.5387	$127.54	$127.55	$127.50
Purchase #2	$91.52	3.434%	$94.6628	$94.66	$94.65	$94.70
Purchase #3	$12.52	3.872%	$13.0048	$13.00	$13.00	$13.00
Purchase #4	$146.48	6.736%	$156.3469	$156.35	$156.35	$156.30
Purchase #5	$201.77	3.461%	$208.7533	$208.75	$208.75	$208.80
Purchase #6	$107.69	10.172%	$118.6442	$118.64	$118.65	$118.60
Purchase #7	$136.30	11.190%	$151.552	$151.55	$151.55	$151.60
7 purchase totals =	$814.54		$870.5027	$870.49	$870.50	$870.50