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	$149.67	4.582%	$156.5279	$156.53	$156.55	$156.50
Purchase #2	$173.93	5.525%	$183.5396	$183.54	$183.55	$183.50
Purchase #3	$71.39	13.390%	$80.9491	$80.95	$80.95	$80.90
Purchase #4	$200.63	11.646%	$223.9954	$224.00	$224.00	$224.00
Purchase #5	$35.69	10.747%	$39.5256	$39.53	$39.55	$39.50
Purchase #6	$45.29	11.592%	$50.54	$50.54	$50.55	$50.50
Purchase #7	$11.73	3.325%	$12.12	$12.12	$12.10	$12.10
7 purchase totals =	$688.33		$747.1976	$747.21	$747.25	$747.00