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	$161.59	6.720%	$172.4488	$172.45	$172.45	$172.40
Purchase #2	$88.48	7.171%	$94.8249	$94.82	$94.80	$94.80
Purchase #3	$206.50	8.179%	$223.3896	$223.39	$223.40	$223.40
Purchase #4	$82.40	12.485%	$92.6876	$92.69	$92.70	$92.70
Purchase #5	$146.47	10.114%	$161.284	$161.28	$161.30	$161.30
Purchase #6	$70.26	11.209%	$78.1354	$78.14	$78.15	$78.10
Purchase #7	$249.61	9.539%	$273.4203	$273.42	$273.40	$273.40
7 purchase totals =	$1,005.31		$1,096.1906	$1,096.19	$1,096.20	$1,096.10