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	$152.81	12.114%	$171.3214	$171.32	$171.30	$171.30
Purchase #2	$84.51	6.838%	$90.2888	$90.29	$90.30	$90.30
Purchase #3	$74.54	11.255%	$82.9295	$82.93	$82.95	$82.90
Purchase #4	$110.82	9.393%	$121.2293	$121.23	$121.25	$121.20
Purchase #5	$62.78	13.646%	$71.347	$71.35	$71.35	$71.30
Purchase #6	$90.86	4.338%	$94.8015	$94.80	$94.80	$94.80
Purchase #7	$94.48	7.243%	$101.3232	$101.32	$101.30	$101.30
7 purchase totals =	$670.80		$733.2407	$733.24	$733.25	$733.10