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	$73.35	4.303%	$76.5063	$76.51	$76.50	$76.50
Purchase #2	$70.30	7.799%	$75.7827	$75.78	$75.80	$75.80
Purchase #3	$153.29	13.801%	$174.4456	$174.45	$174.45	$174.40
Purchase #4	$66.86	8.492%	$72.5378	$72.54	$72.55	$72.50
Purchase #5	$130.27	7.270%	$139.7406	$139.74	$139.75	$139.70
Purchase #6	$46.73	7.705%	$50.3305	$50.33	$50.35	$50.30
Purchase #7	$24.65	3.547%	$25.5243	$25.52	$25.50	$25.50
7 purchase totals =	$565.45		$614.8678	$614.87	$614.90	$614.70