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	$250.49	12.849%	$282.6755	$282.68	$282.70	$282.70
Purchase #2	$63.91	5.303%	$67.2991	$67.30	$67.30	$67.30
Purchase #3	$203.34	11.774%	$227.2813	$227.28	$227.30	$227.30
Purchase #4	$148.39	5.568%	$156.6524	$156.65	$156.65	$156.70
Purchase #5	$39.51	3.313%	$40.819	$40.82	$40.80	$40.80
Purchase #6	$213.59	12.560%	$240.4169	$240.42	$240.40	$240.40
Purchase #7	$155.68	7.454%	$167.2844	$167.28	$167.30	$167.30
7 purchase totals =	$1,074.91		$1,182.4286	$1,182.43	$1,182.45	$1,182.50