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	$49.34	9.198%	$53.8783	$53.88	$53.90	$53.90
Purchase #2	$85.53	3.327%	$88.3756	$88.38	$88.40	$88.40
Purchase #3	$81.89	6.576%	$87.2751	$87.28	$87.30	$87.30
Purchase #4	$53.42	11.399%	$59.5093	$59.51	$59.50	$59.50
Purchase #5	$90.39	9.592%	$99.0602	$99.06	$99.05	$99.10
Purchase #6	$77.87	6.150%	$82.659	$82.66	$82.65	$82.70
Purchase #7	$11.38	13.141%	$12.8754	$12.88	$12.90	$12.90
7 purchase totals =	$449.82		$483.6329	$483.65	$483.70	$483.80