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	$88.78	8.630%	$96.4417	$96.44	$96.45	$96.40
Purchase #2	$68.98	7.193%	$73.9417	$73.94	$73.95	$73.90
Purchase #3	$30.75	13.593%	$34.9298	$34.93	$34.95	$34.90
Purchase #4	$136.30	7.815%	$146.9518	$146.95	$146.95	$147.00
Purchase #5	$71.55	9.514%	$78.3573	$78.36	$78.35	$78.40
Purchase #6	$96.91	3.330%	$100.1371	$100.14	$100.15	$100.10
Purchase #7	$48.81	11.457%	$54.4022	$54.40	$54.40	$54.40
7 purchase totals =	$542.08		$585.1616	$585.16	$585.20	$585.10