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	$104.81	7.557%	$112.7305	$112.73	$112.75	$112.70
Purchase #2	$48.56	13.570%	$55.1496	$55.15	$55.15	$55.10
Purchase #3	$46.76	10.335%	$51.5926	$51.59	$51.60	$51.60
Purchase #4	$37.44	7.716%	$40.3289	$40.33	$40.35	$40.30
Purchase #5	$75.38	9.197%	$82.3127	$82.31	$82.30	$82.30
Purchase #6	$103.36	12.383%	$116.1591	$116.16	$116.15	$116.20
Purchase #7	$198.92	12.809%	$224.3997	$224.40	$224.40	$224.40
7 purchase totals =	$615.23		$682.6731	$682.67	$682.70	$682.60