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	$213.94	5.687%	$226.1068	$226.11	$226.10	$226.10
Purchase #2	$163.51	5.533%	$172.557	$172.56	$172.55	$172.60
Purchase #3	$168.57	7.243%	$180.7795	$180.78	$180.80	$180.80
Purchase #4	$216.60	9.228%	$236.5878	$236.59	$236.60	$236.60
Purchase #5	$126.31	13.349%	$143.1711	$143.17	$143.15	$143.20
Purchase #6	$88.75	4.139%	$92.4234	$92.42	$92.40	$92.40
Purchase #7	$205.59	8.424%	$222.9089	$222.91	$222.90	$222.90
7 purchase totals =	$1,183.27		$1,274.5345	$1,274.54	$1,274.50	$1,274.60