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	$242.36	7.132%	$259.6451	$259.65	$259.65	$259.60
Purchase #2	$89.55	11.176%	$99.5581	$99.56	$99.55	$99.60
Purchase #3	$13.39	11.431%	$14.9206	$14.92	$14.90	$14.90
Purchase #4	$52.95	12.705%	$59.6773	$59.68	$59.70	$59.70
Purchase #5	$209.53	5.785%	$221.6513	$221.65	$221.65	$221.70
Purchase #6	$179.93	6.506%	$191.6362	$191.64	$191.65	$191.60
Purchase #7	$36.25	8.288%	$39.2544	$39.25	$39.25	$39.30
7 purchase totals =	$823.96		$886.3430	$886.35	$886.35	$886.40