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	$190.75	3.860%	$198.113	$198.11	$198.10	$198.10
Purchase #2	$31.37	13.188%	$35.5071	$35.51	$35.50	$35.50
Purchase #3	$43.59	10.343%	$48.0985	$48.10	$48.10	$48.10
Purchase #4	$131.91	5.445%	$139.0925	$139.09	$139.10	$139.10
Purchase #5	$155.53	11.195%	$172.9416	$172.94	$172.95	$172.90
Purchase #6	$180.81	3.769%	$187.6247	$187.62	$187.60	$187.60
Purchase #7	$159.90	3.523%	$165.5333	$165.53	$165.55	$165.50
7 purchase totals =	$893.86		$946.9107	$946.90	$946.90	$946.80