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	$216.48	4.179%	$225.5267	$225.53	$225.55	$225.50
Purchase #2	$120.56	3.174%	$124.3866	$124.39	$124.40	$124.40
Purchase #3	$78.86	13.248%	$89.3074	$89.31	$89.30	$89.30
Purchase #4	$94.75	3.258%	$97.837	$97.84	$97.85	$97.80
Purchase #5	$63.82	5.819%	$67.5337	$67.53	$67.55	$67.50
Purchase #6	$190.60	10.316%	$210.2623	$210.26	$210.25	$210.30
Purchase #7	$129.78	13.371%	$147.1329	$147.13	$147.15	$147.10
7 purchase totals =	$894.85		$961.9866	$961.99	$962.05	$961.90