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	$28.94	3.191%	$29.8635	$29.86	$29.85	$29.90
Purchase #2	$202.43	13.218%	$229.1872	$229.19	$229.20	$229.20
Purchase #3	$200.70	5.573%	$211.885	$211.89	$211.90	$211.90
Purchase #4	$70.62	11.185%	$78.5188	$78.52	$78.50	$78.50
Purchase #5	$234.38	6.858%	$250.4538	$250.45	$250.45	$250.50
Purchase #6	$216.46	13.185%	$245.0003	$245.00	$245.00	$245.00
Purchase #7	$101.86	5.387%	$107.3472	$107.35	$107.35	$107.30
7 purchase totals =	$1,055.39		$1,152.2558	$1,152.26	$1,152.25	$1,152.30