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	$237.38	11.655%	$265.0466	$265.05	$265.05	$265.00
Purchase #2	$90.59	6.146%	$96.1577	$96.16	$96.15	$96.20
Purchase #3	$197.69	10.834%	$219.1077	$219.11	$219.10	$219.10
Purchase #4	$173.91	6.727%	$185.6089	$185.61	$185.60	$185.60
Purchase #5	$217.83	12.746%	$245.5946	$245.59	$245.60	$245.60
Purchase #6	$65.94	11.229%	$73.3444	$73.34	$73.35	$73.30
Purchase #7	$129.44	11.118%	$143.8311	$143.83	$143.85	$143.80
7 purchase totals =	$1,112.78		$1,228.6910	$1,228.69	$1,228.70	$1,228.60