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	$177.28	5.123%	$186.3621	$186.36	$186.35	$186.40
Purchase #2	$100.42	10.542%	$111.0063	$111.01	$111.00	$111.00
Purchase #3	$51.48	12.502%	$57.916	$57.92	$57.90	$57.90
Purchase #4	$147.80	9.735%	$162.1883	$162.19	$162.20	$162.20
Purchase #5	$236.63	7.852%	$255.2102	$255.21	$255.20	$255.20
Purchase #6	$82.56	9.225%	$90.1762	$90.18	$90.20	$90.20
Purchase #7	$197.36	12.632%	$222.2905	$222.29	$222.30	$222.30
7 purchase totals =	$993.53		$1,085.1496	$1,085.16	$1,085.15	$1,085.20