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	$80.79	5.578%	$85.2965	$85.30	$85.30	$85.30
Purchase #2	$205.54	7.630%	$221.2227	$221.22	$221.20	$221.20
Purchase #3	$98.54	6.831%	$105.2713	$105.27	$105.25	$105.30
Purchase #4	$64.35	8.118%	$69.5739	$69.57	$69.55	$69.60
Purchase #5	$201.97	12.593%	$227.4041	$227.40	$227.40	$227.40
Purchase #6	$151.33	11.455%	$168.6649	$168.66	$168.65	$168.70
Purchase #7	$205.40	11.741%	$229.516	$229.52	$229.50	$229.50
7 purchase totals =	$1,007.92		$1,106.9494	$1,106.94	$1,106.85	$1,107.00