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	$212.56	10.511%	$234.9022	$234.90	$234.90	$234.90
Purchase #2	$85.99	7.550%	$92.4822	$92.48	$92.50	$92.50
Purchase #3	$6.45	13.632%	$7.3293	$7.33	$7.35	$7.30
Purchase #4	$47.39	6.600%	$50.5177	$50.52	$50.50	$50.50
Purchase #5	$116.78	12.719%	$131.6332	$131.63	$131.65	$131.60
Purchase #6	$50.64	12.820%	$57.132	$57.13	$57.15	$57.10
Purchase #7	$34.96	12.314%	$39.265	$39.27	$39.25	$39.30
7 purchase totals =	$554.77		$613.2616	$613.26	$613.30	$613.20