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	$239.56	4.203%	$249.6287	$249.63	$249.65	$249.60
Purchase #2	$39.88	8.147%	$43.129	$43.13	$43.15	$43.10
Purchase #3	$63.62	9.315%	$69.5462	$69.55	$69.55	$69.50
Purchase #4	$138.30	10.141%	$152.325	$152.33	$152.35	$152.30
Purchase #5	$243.43	10.763%	$269.6304	$269.63	$269.65	$269.60
Purchase #6	$162.26	11.862%	$181.5073	$181.51	$181.50	$181.50
Purchase #7	$168.48	10.152%	$185.5841	$185.58	$185.60	$185.60
7 purchase totals =	$1,055.53		$1,151.3507	$1,151.36	$1,151.45	$1,151.20