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	$241.86	3.495%	$250.313	$250.31	$250.30	$250.30
Purchase #2	$196.82	3.237%	$203.1911	$203.19	$203.20	$203.20
Purchase #3	$250.37	5.497%	$264.1328	$264.13	$264.15	$264.10
Purchase #4	$42.38	12.470%	$47.6648	$47.66	$47.65	$47.70
Purchase #5	$83.33	8.687%	$90.5689	$90.57	$90.55	$90.60
Purchase #6	$159.99	5.110%	$168.1655	$168.17	$168.15	$168.20
Purchase #7	$152.61	13.109%	$172.6156	$172.62	$172.60	$172.60
7 purchase totals =	$1,127.36		$1,196.6517	$1,196.65	$1,196.60	$1,196.70