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	$149.41	4.829%	$156.625	$156.63	$156.65	$156.60
Purchase #2	$125.90	12.294%	$141.3781	$141.38	$141.40	$141.40
Purchase #3	$147.66	12.315%	$165.8443	$165.84	$165.85	$165.80
Purchase #4	$142.47	6.676%	$151.9813	$151.98	$152.00	$152.00
Purchase #5	$221.39	5.362%	$233.2609	$233.26	$233.25	$233.30
Purchase #6	$36.30	12.783%	$40.9402	$40.94	$40.95	$40.90
Purchase #7	$122.89	13.469%	$139.4421	$139.44	$139.45	$139.40
7 purchase totals =	$946.02		$1,029.4719	$1,029.47	$1,029.55	$1,029.40