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	$184.86	11.477%	$206.0764	$206.08	$206.10	$206.10
Purchase #2	$36.62	11.710%	$40.9082	$40.91	$40.90	$40.90
Purchase #3	$6.36	10.289%	$7.0144	$7.01	$7.00	$7.00
Purchase #4	$219.97	10.867%	$243.8741	$243.87	$243.85	$243.90
Purchase #5	$88.58	3.299%	$91.5023	$91.50	$91.50	$91.50
Purchase #6	$69.25	13.454%	$78.5669	$78.57	$78.55	$78.60
Purchase #7	$139.34	6.825%	$148.85	$148.85	$148.85	$148.90
7 purchase totals =	$744.98		$816.7923	$816.79	$816.75	$816.90