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	$168.57	3.699%	$174.8054	$174.81	$174.80	$174.80
Purchase #2	$49.36	10.794%	$54.6879	$54.69	$54.70	$54.70
Purchase #3	$40.59	5.660%	$42.8874	$42.89	$42.90	$42.90
Purchase #4	$209.56	5.715%	$221.5364	$221.54	$221.55	$221.50
Purchase #5	$242.97	8.310%	$263.1608	$263.16	$263.15	$263.20
Purchase #6	$80.56	8.849%	$87.6888	$87.69	$87.70	$87.70
Purchase #7	$215.58	11.473%	$240.3135	$240.31	$240.30	$240.30
7 purchase totals =	$1,007.19		$1,085.0802	$1,085.09	$1,085.10	$1,085.10