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	$101.79	4.288%	$106.1548	$106.15	$106.15	$106.20
Purchase #2	$201.31	10.670%	$222.7898	$222.79	$222.80	$222.80
Purchase #3	$31.69	4.597%	$33.1468	$33.15	$33.15	$33.10
Purchase #4	$173.29	9.371%	$189.529	$189.53	$189.55	$189.50
Purchase #5	$131.65	4.179%	$137.1517	$137.15	$137.15	$137.20
Purchase #6	$224.44	6.331%	$238.6493	$238.65	$238.65	$238.60
Purchase #7	$148.51	3.436%	$153.6128	$153.61	$153.60	$153.60
7 purchase totals =	$1,012.68		$1,081.0342	$1,081.03	$1,081.05	$1,081.00