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	$31.39	13.132%	$35.5121	$35.51	$35.50	$35.50
Purchase #2	$47.40	11.514%	$52.8576	$52.86	$52.85	$52.90
Purchase #3	$79.65	5.112%	$83.7217	$83.72	$83.70	$83.70
Purchase #4	$11.25	12.109%	$12.6123	$12.61	$12.60	$12.60
Purchase #5	$73.40	4.515%	$76.714	$76.71	$76.70	$76.70
Purchase #6	$81.53	4.749%	$85.4019	$85.40	$85.40	$85.40
Purchase #7	$6.97	7.866%	$7.5183	$7.52	$7.50	$7.50
7 purchase totals =	$331.59		$354.3379	$354.33	$354.25	$354.30