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	$93.83	6.848%	$100.2555	$100.26	$100.25	$100.30
Purchase #2	$20.71	13.824%	$23.573	$23.57	$23.55	$23.60
Purchase #3	$92.28	5.857%	$97.6848	$97.68	$97.70	$97.70
Purchase #4	$89.87	12.134%	$100.7748	$100.77	$100.75	$100.80
Purchase #5	$117.46	11.639%	$131.1312	$131.13	$131.15	$131.10
Purchase #6	$162.71	3.612%	$168.5871	$168.59	$168.60	$168.60
Purchase #7	$54.81	12.214%	$61.5045	$61.50	$61.50	$61.50
7 purchase totals =	$631.67		$683.5109	$683.50	$683.50	$683.60