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	$45.65	10.858%	$50.6067	$50.61	$50.60	$50.60
Purchase #2	$148.27	7.574%	$159.5	$159.50	$159.50	$159.50
Purchase #3	$168.99	7.191%	$181.1421	$181.14	$181.15	$181.10
Purchase #4	$160.29	6.691%	$171.015	$171.02	$171.00	$171.00
Purchase #5	$196.31	8.264%	$212.5331	$212.53	$212.55	$212.50
Purchase #6	$104.38	12.563%	$117.4933	$117.49	$117.50	$117.50
Purchase #7	$182.67	3.675%	$189.3831	$189.38	$189.40	$189.40
7 purchase totals =	$1,006.56		$1,081.6733	$1,081.67	$1,081.70	$1,081.60