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	$74.68	12.382%	$83.9269	$83.93	$83.95	$83.90
Purchase #2	$83.48	8.434%	$90.5207	$90.52	$90.50	$90.50
Purchase #3	$65.50	5.753%	$69.2682	$69.27	$69.25	$69.30
Purchase #4	$112.47	7.415%	$120.8097	$120.81	$120.80	$120.80
Purchase #5	$217.65	7.539%	$234.0586	$234.06	$234.05	$234.10
Purchase #6	$86.28	3.537%	$89.3317	$89.33	$89.35	$89.30
Purchase #7	$73.62	11.237%	$81.8927	$81.89	$81.90	$81.90
7 purchase totals =	$713.68		$769.8085	$769.81	$769.80	$769.80