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	$41.92	13.390%	$47.5331	$47.53	$47.55	$47.50
Purchase #2	$149.72	4.398%	$156.3047	$156.30	$156.30	$156.30
Purchase #3	$235.50	5.657%	$248.8222	$248.82	$248.80	$248.80
Purchase #4	$236.48	13.525%	$268.4639	$268.46	$268.45	$268.50
Purchase #5	$226.92	12.720%	$255.7842	$255.78	$255.80	$255.80
Purchase #6	$226.58	13.599%	$257.3926	$257.39	$257.40	$257.40
Purchase #7	$244.67	8.439%	$265.3177	$265.32	$265.30	$265.30
7 purchase totals =	$1,361.79		$1,499.6184	$1,499.60	$1,499.60	$1,499.60