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	$141.73	11.817%	$158.4782	$158.48	$158.50	$158.50
Purchase #2	$50.41	6.469%	$53.671	$53.67	$53.65	$53.70
Purchase #3	$40.72	3.515%	$42.1513	$42.15	$42.15	$42.20
Purchase #4	$203.36	9.657%	$222.9985	$223.00	$223.00	$223.00
Purchase #5	$159.32	7.389%	$171.0922	$171.09	$171.10	$171.10
Purchase #6	$141.32	13.398%	$160.2541	$160.25	$160.25	$160.30
Purchase #7	$203.52	13.167%	$230.3175	$230.32	$230.30	$230.30
7 purchase totals =	$940.38		$1,038.9628	$1,038.96	$1,038.95	$1,039.10