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	$37.50	11.377%	$41.7664	$41.77	$41.75	$41.80
Purchase #2	$170.76	6.302%	$181.5213	$181.52	$181.50	$181.50
Purchase #3	$68.73	13.726%	$78.1639	$78.16	$78.15	$78.20
Purchase #4	$65.89	5.463%	$69.4896	$69.49	$69.50	$69.50
Purchase #5	$175.87	6.785%	$187.8028	$187.80	$187.80	$187.80
Purchase #6	$69.46	13.289%	$78.6905	$78.69	$78.70	$78.70
Purchase #7	$178.44	9.858%	$196.0306	$196.03	$196.05	$196.00
7 purchase totals =	$766.65		$833.4651	$833.46	$833.45	$833.50