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	$49.89	9.403%	$54.5812	$54.58	$54.60	$54.60
Purchase #2	$130.31	7.316%	$139.8435	$139.84	$139.85	$139.80
Purchase #3	$199.39	8.865%	$217.0659	$217.07	$217.05	$217.10
Purchase #4	$201.35	10.621%	$222.7354	$222.74	$222.75	$222.70
Purchase #5	$90.83	6.342%	$96.5904	$96.59	$96.60	$96.60
Purchase #6	$236.49	7.147%	$253.3919	$253.39	$253.40	$253.40
Purchase #7	$165.46	7.815%	$178.3907	$178.39	$178.40	$178.40
7 purchase totals =	$1,073.72		$1,162.5990	$1,162.60	$1,162.65	$1,162.60