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	$195.87	13.746%	$222.7943	$222.79	$222.80	$222.80
Purchase #2	$54.72	3.187%	$56.4639	$56.46	$56.45	$56.50
Purchase #3	$135.25	11.340%	$150.5874	$150.59	$150.60	$150.60
Purchase #4	$117.35	6.429%	$124.8944	$124.89	$124.90	$124.90
Purchase #5	$66.73	13.547%	$75.7699	$75.77	$75.75	$75.80
Purchase #6	$101.98	6.756%	$108.8698	$108.87	$108.85	$108.90
Purchase #7	$173.82	6.332%	$184.8263	$184.83	$184.85	$184.80
7 purchase totals =	$845.72		$924.2060	$924.20	$924.20	$924.30