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	$43.97	10.504%	$48.5886	$48.59	$48.60	$48.60
Purchase #2	$160.67	4.594%	$168.0512	$168.05	$168.05	$168.10
Purchase #3	$72.35	13.506%	$82.1216	$82.12	$82.10	$82.10
Purchase #4	$113.35	13.473%	$128.6216	$128.62	$128.60	$128.60
Purchase #5	$94.99	4.522%	$99.2854	$99.29	$99.30	$99.30
Purchase #6	$185.52	11.417%	$206.7008	$206.70	$206.70	$206.70
Purchase #7	$197.90	5.490%	$208.7647	$208.76	$208.75	$208.80
7 purchase totals =	$868.75		$942.1339	$942.13	$942.10	$942.20