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	$95.54	12.826%	$107.794	$107.79	$107.80	$107.80
Purchase #2	$59.79	4.108%	$62.2462	$62.25	$62.25	$62.20
Purchase #3	$83.65	4.148%	$87.1198	$87.12	$87.10	$87.10
Purchase #4	$146.26	13.406%	$165.8676	$165.87	$165.85	$165.90
Purchase #5	$189.43	13.723%	$215.4255	$215.43	$215.45	$215.40
Purchase #6	$124.58	10.402%	$137.5388	$137.54	$137.55	$137.50
Purchase #7	$96.84	3.167%	$99.9069	$99.91	$99.90	$99.90
7 purchase totals =	$796.09		$875.8988	$875.91	$875.90	$875.80