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	$37.44	9.365%	$40.9463	$40.95	$40.95	$40.90
Purchase #2	$93.91	5.451%	$99.029	$99.03	$99.05	$99.00
Purchase #3	$186.55	5.502%	$196.814	$196.81	$196.80	$196.80
Purchase #4	$7.43	5.327%	$7.8258	$7.83	$7.85	$7.80
Purchase #5	$123.41	6.800%	$131.8019	$131.80	$131.80	$131.80
Purchase #6	$194.87	9.794%	$213.9556	$213.96	$213.95	$214.00
Purchase #7	$175.35	11.615%	$195.7169	$195.72	$195.70	$195.70
7 purchase totals =	$818.96		$886.0895	$886.10	$886.10	$886.00