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	$43.48	11.685%	$48.5606	$48.56	$48.55	$48.60
Purchase #2	$162.40	8.626%	$176.4086	$176.41	$176.40	$176.40
Purchase #3	$129.90	11.327%	$144.6138	$144.61	$144.60	$144.60
Purchase #4	$242.51	6.450%	$258.1519	$258.15	$258.15	$258.20
Purchase #5	$199.45	6.245%	$211.9057	$211.91	$211.90	$211.90
Purchase #6	$237.38	7.870%	$256.0618	$256.06	$256.05	$256.10
Purchase #7	$149.67	5.603%	$158.056	$158.06	$158.05	$158.10
7 purchase totals =	$1,164.79		$1,253.7584	$1,253.76	$1,253.70	$1,253.90