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	$171.67	7.633%	$184.7736	$184.77	$184.75	$184.80
Purchase #2	$189.53	12.175%	$212.6053	$212.61	$212.60	$212.60
Purchase #3	$46.95	9.281%	$51.3074	$51.31	$51.30	$51.30
Purchase #4	$52.53	12.490%	$59.091	$59.09	$59.10	$59.10
Purchase #5	$173.91	8.676%	$188.9984	$189.00	$189.00	$189.00
Purchase #6	$35.77	12.259%	$40.155	$40.16	$40.15	$40.20
Purchase #7	$12.96	11.838%	$14.4942	$14.49	$14.50	$14.50
7 purchase totals =	$683.32		$751.4249	$751.43	$751.40	$751.50