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	$216.97	3.397%	$224.3405	$224.34	$224.35	$224.30
Purchase #2	$186.59	11.551%	$208.143	$208.14	$208.15	$208.10
Purchase #3	$219.54	6.715%	$234.2821	$234.28	$234.30	$234.30
Purchase #4	$40.64	11.650%	$45.3746	$45.37	$45.35	$45.40
Purchase #5	$102.73	5.329%	$108.2045	$108.20	$108.20	$108.20
Purchase #6	$122.49	4.180%	$127.6101	$127.61	$127.60	$127.60
Purchase #7	$167.41	7.287%	$179.6092	$179.61	$179.60	$179.60
7 purchase totals =	$1,056.37		$1,127.5640	$1,127.55	$1,127.55	$1,127.50