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	$63.45	4.516%	$66.3154	$66.32	$66.30	$66.30
Purchase #2	$59.62	8.297%	$64.5667	$64.57	$64.55	$64.60
Purchase #3	$175.35	7.241%	$188.0471	$188.05	$188.05	$188.00
Purchase #4	$5.90	13.398%	$6.6905	$6.69	$6.70	$6.70
Purchase #5	$69.64	3.579%	$72.1324	$72.13	$72.15	$72.10
Purchase #6	$28.42	13.658%	$32.3016	$32.30	$32.30	$32.30
Purchase #7	$57.39	13.803%	$65.3115	$65.31	$65.30	$65.30
7 purchase totals =	$459.77		$495.3652	$495.37	$495.35	$495.30