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	$46.60	11.819%	$52.1077	$52.11	$52.10	$52.10
Purchase #2	$137.68	7.516%	$148.028	$148.03	$148.05	$148.00
Purchase #3	$107.31	4.110%	$111.7204	$111.72	$111.70	$111.70
Purchase #4	$130.78	12.427%	$147.032	$147.03	$147.05	$147.00
Purchase #5	$143.79	6.104%	$152.5669	$152.57	$152.55	$152.60
Purchase #6	$162.72	13.874%	$185.2958	$185.30	$185.30	$185.30
Purchase #7	$107.50	12.312%	$120.7354	$120.74	$120.75	$120.70
7 purchase totals =	$836.38		$917.4862	$917.50	$917.50	$917.40