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	$104.44	4.815%	$109.4688	$109.47	$109.45	$109.50
Purchase #2	$195.81	5.283%	$206.1546	$206.15	$206.15	$206.20
Purchase #3	$75.62	9.128%	$82.5226	$82.52	$82.50	$82.50
Purchase #4	$63.41	6.552%	$67.5646	$67.56	$67.55	$67.60
Purchase #5	$169.48	9.686%	$185.8958	$185.90	$185.90	$185.90
Purchase #6	$56.89	10.388%	$62.7997	$62.80	$62.80	$62.80
Purchase #7	$31.50	10.196%	$34.7117	$34.71	$34.70	$34.70
7 purchase totals =	$697.15		$749.1178	$749.11	$749.05	$749.20