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	$73.55	3.859%	$76.3883	$76.39	$76.40	$76.40
Purchase #2	$148.83	4.508%	$155.5393	$155.54	$155.55	$155.50
Purchase #3	$79.40	13.102%	$89.803	$89.80	$89.80	$89.80
Purchase #4	$48.88	5.539%	$51.5875	$51.59	$51.60	$51.60
Purchase #5	$58.40	9.431%	$63.9077	$63.91	$63.90	$63.90
Purchase #6	$52.26	6.353%	$55.5801	$55.58	$55.60	$55.60
Purchase #7	$244.96	13.254%	$277.427	$277.43	$277.45	$277.40
7 purchase totals =	$706.28		$770.2329	$770.24	$770.30	$770.20