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	$157.38	12.630%	$177.2571	$177.26	$177.25	$177.30
Purchase #2	$89.72	11.781%	$100.2899	$100.29	$100.30	$100.30
Purchase #3	$165.34	4.260%	$172.3835	$172.38	$172.40	$172.40
Purchase #4	$181.32	6.785%	$193.6226	$193.62	$193.60	$193.60
Purchase #5	$51.61	3.759%	$53.55	$53.55	$53.55	$53.60
Purchase #6	$155.65	10.303%	$171.6866	$171.69	$171.70	$171.70
Purchase #7	$87.69	5.428%	$92.4498	$92.45	$92.45	$92.40
7 purchase totals =	$888.71		$961.2395	$961.24	$961.25	$961.30