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	$39.40	12.111%	$44.1717	$44.17	$44.15	$44.20
Purchase #2	$39.77	10.238%	$43.8417	$43.84	$43.85	$43.80
Purchase #3	$143.53	5.222%	$151.0251	$151.03	$151.05	$151.00
Purchase #4	$169.68	9.298%	$185.4568	$185.46	$185.45	$185.50
Purchase #5	$89.65	6.808%	$95.7534	$95.75	$95.75	$95.80
Purchase #6	$109.99	9.314%	$120.2345	$120.23	$120.25	$120.20
Purchase #7	$85.27	6.410%	$90.7358	$90.74	$90.75	$90.70
7 purchase totals =	$677.29		$731.2190	$731.22	$731.25	$731.20