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	$89.66	3.750%	$93.0223	$93.02	$93.00	$93.00
Purchase #2	$130.90	10.230%	$144.2911	$144.29	$144.30	$144.30
Purchase #3	$197.39	11.229%	$219.5549	$219.55	$219.55	$219.60
Purchase #4	$43.96	4.710%	$46.0305	$46.03	$46.05	$46.00
Purchase #5	$79.47	7.428%	$85.373	$85.37	$85.35	$85.40
Purchase #6	$200.89	4.763%	$210.4584	$210.46	$210.45	$210.50
Purchase #7	$227.80	12.646%	$256.6076	$256.61	$256.60	$256.60
7 purchase totals =	$970.07		$1,055.3378	$1,055.33	$1,055.30	$1,055.40