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	$231.30	5.731%	$244.5558	$244.56	$244.55	$244.60
Purchase #2	$221.90	13.395%	$251.6235	$251.62	$251.60	$251.60
Purchase #3	$250.96	13.542%	$284.945	$284.95	$284.95	$284.90
Purchase #4	$97.84	5.588%	$103.3073	$103.31	$103.30	$103.30
Purchase #5	$79.42	13.479%	$90.125	$90.13	$90.15	$90.10
Purchase #6	$120.69	5.421%	$127.2326	$127.23	$127.25	$127.20
Purchase #7	$132.48	7.746%	$142.7419	$142.74	$142.75	$142.70
7 purchase totals =	$1,134.59		$1,244.5311	$1,244.54	$1,244.55	$1,244.40