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	$237.98	5.129%	$250.186	$250.19	$250.20	$250.20
Purchase #2	$239.91	6.433%	$255.3434	$255.34	$255.35	$255.30
Purchase #3	$217.25	11.196%	$241.5733	$241.57	$241.55	$241.60
Purchase #4	$132.29	13.495%	$150.1425	$150.14	$150.15	$150.10
Purchase #5	$93.89	13.874%	$106.9163	$106.92	$106.90	$106.90
Purchase #6	$27.29	3.401%	$28.2181	$28.22	$28.20	$28.20
Purchase #7	$80.74	12.409%	$90.759	$90.76	$90.75	$90.80
7 purchase totals =	$1,029.35		$1,123.1386	$1,123.14	$1,123.10	$1,123.10