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	$148.50	6.570%	$158.2565	$158.26	$158.25	$158.30
Purchase #2	$83.75	6.669%	$89.3353	$89.34	$89.35	$89.30
Purchase #3	$187.41	12.742%	$211.2898	$211.29	$211.30	$211.30
Purchase #4	$154.33	11.515%	$172.1011	$172.10	$172.10	$172.10
Purchase #5	$247.87	12.222%	$278.1647	$278.16	$278.15	$278.20
Purchase #6	$29.49	6.160%	$31.3066	$31.31	$31.30	$31.30
Purchase #7	$193.60	12.773%	$218.3285	$218.33	$218.35	$218.30
7 purchase totals =	$1,044.95		$1,158.7825	$1,158.79	$1,158.80	$1,158.80