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	$167.77	13.685%	$190.7293	$190.73	$190.75	$190.70
Purchase #2	$243.85	11.352%	$271.5319	$271.53	$271.55	$271.50
Purchase #3	$214.81	8.677%	$233.4491	$233.45	$233.45	$233.40
Purchase #4	$212.93	5.146%	$223.8874	$223.89	$223.90	$223.90
Purchase #5	$25.75	7.702%	$27.7333	$27.73	$27.75	$27.70
Purchase #6	$116.38	3.350%	$120.2787	$120.28	$120.30	$120.30
Purchase #7	$88.43	7.683%	$95.2241	$95.22	$95.20	$95.20
7 purchase totals =	$1,069.92		$1,162.8338	$1,162.83	$1,162.90	$1,162.70