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	$45.96	8.688%	$49.953	$49.95	$49.95	$50.00
Purchase #2	$84.67	6.612%	$90.2684	$90.27	$90.25	$90.30
Purchase #3	$118.93	5.496%	$125.4664	$125.47	$125.45	$125.50
Purchase #4	$190.72	4.486%	$199.2757	$199.28	$199.30	$199.30
Purchase #5	$80.73	5.859%	$85.46	$85.46	$85.45	$85.50
Purchase #6	$43.76	8.432%	$47.4498	$47.45	$47.45	$47.40
Purchase #7	$126.91	8.376%	$137.54	$137.54	$137.55	$137.50
7 purchase totals =	$691.68		$735.4133	$735.42	$735.40	$735.50