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	$54.83	6.872%	$58.5979	$58.60	$58.60	$58.60
Purchase #2	$20.95	7.805%	$22.5851	$22.59	$22.60	$22.60
Purchase #3	$184.81	3.338%	$190.979	$190.98	$191.00	$191.00
Purchase #4	$241.28	9.580%	$264.3946	$264.39	$264.40	$264.40
Purchase #5	$56.44	5.686%	$59.6492	$59.65	$59.65	$59.60
Purchase #6	$28.69	9.637%	$31.4549	$31.45	$31.45	$31.50
Purchase #7	$46.61	5.443%	$49.147	$49.15	$49.15	$49.10
7 purchase totals =	$633.61		$676.8077	$676.81	$676.85	$676.80