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	$92.42	3.560%	$95.7102	$95.71	$95.70	$95.70
Purchase #2	$45.67	3.199%	$47.131	$47.13	$47.15	$47.10
Purchase #3	$67.40	6.687%	$71.907	$71.91	$71.90	$71.90
Purchase #4	$92.95	8.558%	$100.9047	$100.90	$100.90	$100.90
Purchase #5	$122.66	9.423%	$134.2183	$134.22	$134.20	$134.20
Purchase #6	$159.64	5.771%	$168.8528	$168.85	$168.85	$168.90
Purchase #7	$116.92	12.439%	$131.4637	$131.46	$131.45	$131.50
7 purchase totals =	$697.66		$750.1877	$750.18	$750.15	$750.20