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	$202.66	10.230%	$223.3921	$223.39	$223.40	$223.40
Purchase #2	$37.85	9.483%	$41.4393	$41.44	$41.45	$41.40
Purchase #3	$45.32	6.160%	$48.1117	$48.11	$48.10	$48.10
Purchase #4	$107.29	4.142%	$111.734	$111.73	$111.75	$111.70
Purchase #5	$105.46	3.465%	$109.1142	$109.11	$109.10	$109.10
Purchase #6	$52.49	13.814%	$59.741	$59.74	$59.75	$59.70
Purchase #7	$176.41	4.291%	$183.9798	$183.98	$184.00	$184.00
7 purchase totals =	$727.48		$777.5121	$777.50	$777.55	$777.40