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	$235.51	8.228%	$254.8878	$254.89	$254.90	$254.90
Purchase #2	$147.71	6.873%	$157.8621	$157.86	$157.85	$157.90
Purchase #3	$195.44	11.782%	$218.4667	$218.47	$218.45	$218.50
Purchase #4	$101.40	13.274%	$114.8598	$114.86	$114.85	$114.90
Purchase #5	$75.53	3.401%	$78.0988	$78.10	$78.10	$78.10
Purchase #6	$229.28	7.281%	$245.9739	$245.97	$245.95	$246.00
Purchase #7	$53.54	7.480%	$57.5448	$57.54	$57.55	$57.50
7 purchase totals =	$1,038.41		$1,127.6939	$1,127.69	$1,127.65	$1,127.80