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	$95.41	9.651%	$104.618	$104.62	$104.60	$104.60
Purchase #2	$52.93	8.746%	$57.5593	$57.56	$57.55	$57.60
Purchase #3	$17.80	6.211%	$18.9056	$18.91	$18.90	$18.90
Purchase #4	$250.31	10.111%	$275.6188	$275.62	$275.60	$275.60
Purchase #5	$172.74	13.571%	$196.1825	$196.18	$196.20	$196.20
Purchase #6	$75.59	8.612%	$82.0998	$82.10	$82.10	$82.10
Purchase #7	$238.55	3.181%	$246.1383	$246.14	$246.15	$246.10
7 purchase totals =	$903.33		$981.1223	$981.13	$981.10	$981.10