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	$80.74	6.264%	$85.7976	$85.80	$85.80	$85.80
Purchase #2	$82.60	4.230%	$86.094	$86.09	$86.10	$86.10
Purchase #3	$28.66	12.558%	$32.2591	$32.26	$32.25	$32.30
Purchase #4	$189.56	3.648%	$196.4751	$196.48	$196.50	$196.50
Purchase #5	$222.92	5.732%	$235.6978	$235.70	$235.70	$235.70
Purchase #6	$220.32	7.508%	$236.8616	$236.86	$236.85	$236.90
Purchase #7	$218.90	11.746%	$244.612	$244.61	$244.60	$244.60
7 purchase totals =	$1,043.70		$1,117.7972	$1,117.80	$1,117.80	$1,117.90