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	$210.27	12.115%	$235.7442	$235.74	$235.75	$235.70
Purchase #2	$195.60	6.666%	$208.6387	$208.64	$208.65	$208.60
Purchase #3	$78.54	8.770%	$85.428	$85.43	$85.45	$85.40
Purchase #4	$189.44	3.405%	$195.8904	$195.89	$195.90	$195.90
Purchase #5	$241.64	12.315%	$271.398	$271.40	$271.40	$271.40
Purchase #6	$50.49	7.497%	$54.2752	$54.28	$54.30	$54.30
Purchase #7	$82.90	9.440%	$90.7258	$90.73	$90.75	$90.70
7 purchase totals =	$1,048.88		$1,142.1003	$1,142.11	$1,142.20	$1,142.00