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	$160.55	3.291%	$165.8337	$165.83	$165.85	$165.80
Purchase #2	$55.65	6.300%	$59.156	$59.16	$59.15	$59.20
Purchase #3	$106.73	6.138%	$113.2811	$113.28	$113.30	$113.30
Purchase #4	$228.65	11.816%	$255.6673	$255.67	$255.65	$255.70
Purchase #5	$71.39	5.410%	$75.2522	$75.25	$75.25	$75.30
Purchase #6	$113.94	6.859%	$121.7551	$121.76	$121.75	$121.80
Purchase #7	$205.50	5.263%	$216.3155	$216.32	$216.30	$216.30
7 purchase totals =	$942.41		$1,007.2609	$1,007.27	$1,007.25	$1,007.40