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	$114.37	4.594%	$119.6242	$119.62	$119.60	$119.60
Purchase #2	$211.27	8.796%	$229.8533	$229.85	$229.85	$229.90
Purchase #3	$75.62	8.144%	$81.7785	$81.78	$81.80	$81.80
Purchase #4	$133.73	6.796%	$142.8183	$142.82	$142.80	$142.80
Purchase #5	$198.86	6.667%	$212.118	$212.12	$212.10	$212.10
Purchase #6	$211.61	11.325%	$235.5748	$235.57	$235.55	$235.60
Purchase #7	$33.49	13.192%	$37.908	$37.91	$37.90	$37.90
7 purchase totals =	$978.95		$1,059.6751	$1,059.67	$1,059.60	$1,059.70