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	$57.78	12.113%	$64.7789	$64.78	$64.80	$64.80
Purchase #2	$119.41	6.494%	$127.1645	$127.16	$127.15	$127.20
Purchase #3	$193.41	13.692%	$219.8917	$219.89	$219.90	$219.90
Purchase #4	$232.82	3.259%	$240.4076	$240.41	$240.40	$240.40
Purchase #5	$84.69	8.325%	$91.7404	$91.74	$91.75	$91.70
Purchase #6	$159.61	3.752%	$165.5986	$165.60	$165.60	$165.60
Purchase #7	$172.70	8.227%	$186.908	$186.91	$186.90	$186.90
7 purchase totals =	$1,020.42		$1,096.4897	$1,096.49	$1,096.50	$1,096.50