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	$205.58	9.666%	$225.4514	$225.45	$225.45	$225.50
Purchase #2	$169.73	9.241%	$185.4147	$185.41	$185.40	$185.40
Purchase #3	$239.76	11.484%	$267.294	$267.29	$267.30	$267.30
Purchase #4	$80.45	11.575%	$89.7621	$89.76	$89.75	$89.80
Purchase #5	$43.46	12.364%	$48.8334	$48.83	$48.85	$48.80
Purchase #6	$116.30	11.539%	$129.7199	$129.72	$129.70	$129.70
Purchase #7	$186.46	11.735%	$208.3411	$208.34	$208.35	$208.30
7 purchase totals =	$1,041.74		$1,154.8166	$1,154.80	$1,154.80	$1,154.80