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	$64.34	13.103%	$72.7705	$72.77	$72.75	$72.80
Purchase #2	$156.88	11.849%	$175.4687	$175.47	$175.45	$175.50
Purchase #3	$82.31	9.705%	$90.2982	$90.30	$90.30	$90.30
Purchase #4	$250.31	13.617%	$284.3947	$284.39	$284.40	$284.40
Purchase #5	$202.47	8.859%	$220.4068	$220.41	$220.40	$220.40
Purchase #6	$104.48	7.699%	$112.5239	$112.52	$112.50	$112.50
Purchase #7	$167.94	12.442%	$188.8351	$188.84	$188.85	$188.80
7 purchase totals =	$1,028.73		$1,144.6979	$1,144.70	$1,144.65	$1,144.70