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	$73.88	12.480%	$83.1002	$83.10	$83.10	$83.10
Purchase #2	$34.99	7.439%	$37.5929	$37.59	$37.60	$37.60
Purchase #3	$73.29	6.828%	$78.2942	$78.29	$78.30	$78.30
Purchase #4	$86.35	9.104%	$94.2113	$94.21	$94.20	$94.20
Purchase #5	$67.83	3.626%	$70.2895	$70.29	$70.30	$70.30
Purchase #6	$191.25	4.727%	$200.2904	$200.29	$200.30	$200.30
Purchase #7	$165.58	4.156%	$172.4615	$172.46	$172.45	$172.50
7 purchase totals =	$693.17		$736.2400	$736.23	$736.25	$736.30