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	$53.51	11.110%	$59.455	$59.46	$59.45	$59.50
Purchase #2	$171.66	7.791%	$185.034	$185.03	$185.05	$185.00
Purchase #3	$195.38	8.414%	$211.8193	$211.82	$211.80	$211.80
Purchase #4	$176.51	12.789%	$199.0839	$199.08	$199.10	$199.10
Purchase #5	$190.72	4.530%	$199.3596	$199.36	$199.35	$199.40
Purchase #6	$199.87	4.206%	$208.2765	$208.28	$208.30	$208.30
Purchase #7	$76.88	3.303%	$79.4193	$79.42	$79.40	$79.40
7 purchase totals =	$1,064.53		$1,142.4476	$1,142.45	$1,142.45	$1,142.50