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	$166.75	3.227%	$172.131	$172.13	$172.15	$172.10
Purchase #2	$162.92	11.800%	$182.1446	$182.14	$182.15	$182.10
Purchase #3	$58.62	4.428%	$61.2157	$61.22	$61.20	$61.20
Purchase #4	$107.96	10.414%	$119.203	$119.20	$119.20	$119.20
Purchase #5	$84.97	5.184%	$89.3748	$89.37	$89.35	$89.40
Purchase #6	$226.81	8.361%	$245.7736	$245.77	$245.75	$245.80
Purchase #7	$164.81	4.380%	$172.0287	$172.03	$172.05	$172.00
7 purchase totals =	$972.84		$1,041.8714	$1,041.86	$1,041.85	$1,041.80