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	$238.65	13.391%	$270.6076	$270.61	$270.60	$270.60
Purchase #2	$59.79	10.843%	$66.273	$66.27	$66.25	$66.30
Purchase #3	$107.40	10.837%	$119.0389	$119.04	$119.05	$119.00
Purchase #4	$189.27	3.186%	$195.3001	$195.30	$195.30	$195.30
Purchase #5	$75.50	4.809%	$79.1308	$79.13	$79.15	$79.10
Purchase #6	$247.72	5.371%	$261.025	$261.03	$261.05	$261.00
Purchase #7	$82.81	9.398%	$90.5925	$90.59	$90.60	$90.60
7 purchase totals =	$1,001.14		$1,081.9679	$1,081.97	$1,082.00	$1,081.90