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	$103.50	7.475%	$111.2366	$111.24	$111.25	$111.20
Purchase #2	$125.53	3.406%	$129.8056	$129.81	$129.80	$129.80
Purchase #3	$86.58	3.221%	$89.3687	$89.37	$89.35	$89.40
Purchase #4	$164.32	9.373%	$179.7217	$179.72	$179.70	$179.70
Purchase #5	$149.93	13.308%	$169.8827	$169.88	$169.90	$169.90
Purchase #6	$39.70	10.424%	$43.8383	$43.84	$43.85	$43.80
Purchase #7	$92.59	6.330%	$98.4509	$98.45	$98.45	$98.50
7 purchase totals =	$762.15		$822.3045	$822.31	$822.30	$822.30