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	$51.82	5.143%	$54.4851	$54.49	$54.50	$54.50
Purchase #2	$173.94	9.632%	$190.6939	$190.69	$190.70	$190.70
Purchase #3	$61.25	12.463%	$68.8836	$68.88	$68.90	$68.90
Purchase #4	$28.50	10.214%	$31.411	$31.41	$31.40	$31.40
Purchase #5	$213.42	10.180%	$235.1462	$235.15	$235.15	$235.10
Purchase #6	$99.30	13.104%	$112.3123	$112.31	$112.30	$112.30
Purchase #7	$245.30	11.746%	$274.1129	$274.11	$274.10	$274.10
7 purchase totals =	$873.53		$967.0450	$967.04	$967.05	$967.00