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	$154.47	12.407%	$173.6351	$173.64	$173.65	$173.60
Purchase #2	$174.41	9.161%	$190.3877	$190.39	$190.40	$190.40
Purchase #3	$131.84	7.612%	$141.8757	$141.88	$141.90	$141.90
Purchase #4	$183.29	9.530%	$200.7575	$200.76	$200.75	$200.80
Purchase #5	$196.86	12.857%	$222.1703	$222.17	$222.15	$222.20
Purchase #6	$86.63	9.403%	$94.7758	$94.78	$94.80	$94.80
Purchase #7	$53.51	9.437%	$58.5597	$58.56	$58.55	$58.60
7 purchase totals =	$981.01		$1,082.1618	$1,082.18	$1,082.20	$1,082.30