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	$211.38	13.776%	$240.4997	$240.50	$240.50	$240.50
Purchase #2	$29.94	6.157%	$31.7834	$31.78	$31.80	$31.80
Purchase #3	$184.46	6.344%	$196.1621	$196.16	$196.15	$196.20
Purchase #4	$250.51	7.616%	$269.5888	$269.59	$269.60	$269.60
Purchase #5	$171.64	8.200%	$185.7145	$185.71	$185.70	$185.70
Purchase #6	$208.66	4.368%	$217.7743	$217.77	$217.75	$217.80
Purchase #7	$175.90	4.501%	$183.8173	$183.82	$183.80	$183.80
7 purchase totals =	$1,232.49		$1,325.3401	$1,325.33	$1,325.30	$1,325.40