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	$172.85	10.454%	$190.9197	$190.92	$190.90	$190.90
Purchase #2	$147.66	11.397%	$164.4888	$164.49	$164.50	$164.50
Purchase #3	$133.55	9.240%	$145.89	$145.89	$145.90	$145.90
Purchase #4	$50.52	10.734%	$55.9428	$55.94	$55.95	$55.90
Purchase #5	$27.97	9.196%	$30.5421	$30.54	$30.55	$30.50
Purchase #6	$181.76	6.519%	$193.6089	$193.61	$193.60	$193.60
Purchase #7	$206.28	11.549%	$230.1033	$230.10	$230.10	$230.10
7 purchase totals =	$920.59		$1,011.4956	$1,011.49	$1,011.50	$1,011.40