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	$122.56	7.598%	$131.8721	$131.87	$131.85	$131.90
Purchase #2	$189.29	4.562%	$197.9254	$197.93	$197.95	$197.90
Purchase #3	$136.43	4.365%	$142.3852	$142.39	$142.40	$142.40
Purchase #4	$228.34	11.551%	$254.7156	$254.72	$254.70	$254.70
Purchase #5	$236.46	11.213%	$262.9743	$262.97	$262.95	$263.00
Purchase #6	$90.87	8.861%	$98.922	$98.92	$98.90	$98.90
Purchase #7	$53.48	5.615%	$56.4829	$56.48	$56.50	$56.50
7 purchase totals =	$1,057.43		$1,145.2775	$1,145.28	$1,145.25	$1,145.30