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	$120.59	9.140%	$131.6119	$131.61	$131.60	$131.60
Purchase #2	$25.81	10.323%	$28.4744	$28.47	$28.45	$28.50
Purchase #3	$24.95	8.502%	$27.0712	$27.07	$27.05	$27.10
Purchase #4	$146.73	5.586%	$154.9263	$154.93	$154.95	$154.90
Purchase #5	$222.88	5.335%	$234.7706	$234.77	$234.75	$234.80
Purchase #6	$193.45	3.705%	$200.6173	$200.62	$200.60	$200.60
Purchase #7	$215.85	8.148%	$233.4375	$233.44	$233.45	$233.40
7 purchase totals =	$950.26		$1,010.9092	$1,010.91	$1,010.85	$1,010.90