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	$146.33	12.855%	$165.1407	$165.14	$165.15	$165.10
Purchase #2	$54.70	12.417%	$61.4921	$61.49	$61.50	$61.50
Purchase #3	$200.79	7.850%	$216.552	$216.55	$216.55	$216.60
Purchase #4	$184.44	5.837%	$195.2058	$195.21	$195.20	$195.20
Purchase #5	$126.81	3.662%	$131.4538	$131.45	$131.45	$131.50
Purchase #6	$172.44	8.523%	$187.1371	$187.14	$187.15	$187.10
Purchase #7	$96.52	6.870%	$103.1509	$103.15	$103.15	$103.20
7 purchase totals =	$982.03		$1,060.1324	$1,060.13	$1,060.15	$1,060.20