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	$174.33	3.211%	$179.9277	$179.93	$179.95	$179.90
Purchase #2	$18.65	13.592%	$21.1849	$21.18	$21.20	$21.20
Purchase #3	$109.64	6.323%	$116.5725	$116.57	$116.55	$116.60
Purchase #4	$203.32	3.861%	$211.1702	$211.17	$211.15	$211.20
Purchase #5	$121.55	7.752%	$130.9726	$130.97	$130.95	$131.00
Purchase #6	$125.71	4.298%	$131.113	$131.11	$131.10	$131.10
Purchase #7	$147.65	13.262%	$167.2313	$167.23	$167.25	$167.20
7 purchase totals =	$900.85		$958.1722	$958.16	$958.15	$958.20