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	$247.28	6.702%	$263.8527	$263.85	$263.85	$263.90
Purchase #2	$76.93	5.120%	$80.8688	$80.87	$80.85	$80.90
Purchase #3	$89.96	10.264%	$99.1935	$99.19	$99.20	$99.20
Purchase #4	$27.78	9.405%	$30.3927	$30.39	$30.40	$30.40
Purchase #5	$158.64	7.609%	$170.7109	$170.71	$170.70	$170.70
Purchase #6	$84.85	5.310%	$89.3555	$89.36	$89.35	$89.40
Purchase #7	$88.57	12.790%	$99.8981	$99.90	$99.90	$99.90
7 purchase totals =	$774.01		$834.2722	$834.27	$834.25	$834.40