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	$165.37	4.140%	$172.2163	$172.22	$172.20	$172.20
Purchase #2	$171.85	9.247%	$187.741	$187.74	$187.75	$187.70
Purchase #3	$210.50	3.234%	$217.3076	$217.31	$217.30	$217.30
Purchase #4	$174.98	5.500%	$184.6039	$184.60	$184.60	$184.60
Purchase #5	$102.81	7.394%	$110.4118	$110.41	$110.40	$110.40
Purchase #6	$35.69	7.521%	$38.3742	$38.37	$38.35	$38.40
Purchase #7	$89.98	11.111%	$99.9777	$99.98	$100.00	$100.00
7 purchase totals =	$951.18		$1,010.6325	$1,010.63	$1,010.60	$1,010.60