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	$54.40	13.199%	$61.5803	$61.58	$61.60	$61.60
Purchase #2	$45.92	9.279%	$50.1809	$50.18	$50.20	$50.20
Purchase #3	$78.40	6.352%	$83.38	$83.38	$83.40	$83.40
Purchase #4	$101.46	3.165%	$104.6712	$104.67	$104.65	$104.70
Purchase #5	$140.26	8.298%	$151.8988	$151.90	$151.90	$151.90
Purchase #6	$136.67	10.362%	$150.8317	$150.83	$150.85	$150.80
Purchase #7	$188.55	11.781%	$210.7631	$210.76	$210.75	$210.80
7 purchase totals =	$745.66		$813.3060	$813.30	$813.35	$813.40