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	$20.67	6.516%	$22.0169	$22.02	$22.00	$22.00
Purchase #2	$242.52	7.396%	$260.4568	$260.46	$260.45	$260.50
Purchase #3	$218.39	10.191%	$240.6461	$240.65	$240.65	$240.60
Purchase #4	$175.30	8.264%	$189.7868	$189.79	$189.80	$189.80
Purchase #5	$183.91	6.824%	$196.46	$196.46	$196.45	$196.50
Purchase #6	$177.58	7.728%	$191.3034	$191.30	$191.30	$191.30
Purchase #7	$155.54	6.385%	$165.4712	$165.47	$165.45	$165.50
7 purchase totals =	$1,173.91		$1,266.1412	$1,266.15	$1,266.10	$1,266.20