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	$223.90	9.825%	$245.8982	$245.90	$245.90	$245.90
Purchase #2	$231.81	7.426%	$249.0242	$249.02	$249.00	$249.00
Purchase #3	$95.44	5.772%	$100.9488	$100.95	$100.95	$100.90
Purchase #4	$195.58	13.824%	$222.617	$222.62	$222.60	$222.60
Purchase #5	$101.28	10.317%	$111.7291	$111.73	$111.75	$111.70
Purchase #6	$245.37	5.418%	$258.6641	$258.66	$258.65	$258.70
Purchase #7	$93.25	11.354%	$103.8376	$103.84	$103.85	$103.80
7 purchase totals =	$1,186.63		$1,292.7190	$1,292.72	$1,292.70	$1,292.60