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	$105.62	5.140%	$111.0489	$111.05	$111.05	$111.00
Purchase #2	$36.62	8.814%	$39.8477	$39.85	$39.85	$39.80
Purchase #3	$137.28	4.446%	$143.3835	$143.38	$143.40	$143.40
Purchase #4	$162.96	12.780%	$183.7863	$183.79	$183.80	$183.80
Purchase #5	$238.71	7.199%	$255.8947	$255.89	$255.90	$255.90
Purchase #6	$146.53	6.129%	$155.5108	$155.51	$155.50	$155.50
Purchase #7	$113.37	7.682%	$122.0791	$122.08	$122.10	$122.10
7 purchase totals =	$941.09		$1,011.5510	$1,011.55	$1,011.60	$1,011.50