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	$42.26	9.687%	$46.3537	$46.35	$46.35	$46.40
Purchase #2	$245.95	10.298%	$271.2779	$271.28	$271.30	$271.30
Purchase #3	$147.27	11.731%	$164.5462	$164.55	$164.55	$164.50
Purchase #4	$83.50	4.787%	$87.4971	$87.50	$87.50	$87.50
Purchase #5	$70.37	8.756%	$76.5316	$76.53	$76.55	$76.50
Purchase #6	$240.45	3.297%	$248.3776	$248.38	$248.40	$248.40
Purchase #7	$43.45	10.178%	$47.8723	$47.87	$47.85	$47.90
7 purchase totals =	$873.25		$942.4564	$942.46	$942.50	$942.50