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	$84.59	9.301%	$92.4577	$92.46	$92.45	$92.50
Purchase #2	$139.58	4.807%	$146.2896	$146.29	$146.30	$146.30
Purchase #3	$36.88	4.681%	$38.6064	$38.61	$38.60	$38.60
Purchase #4	$159.69	8.183%	$172.7574	$172.76	$172.75	$172.80
Purchase #5	$245.91	11.105%	$273.2183	$273.22	$273.20	$273.20
Purchase #6	$216.35	6.190%	$229.7421	$229.74	$229.75	$229.70
Purchase #7	$42.89	6.511%	$45.6826	$45.68	$45.70	$45.70
7 purchase totals =	$925.89		$998.7541	$998.76	$998.75	$998.80