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	$175.62	10.764%	$194.5237	$194.52	$194.50	$194.50
Purchase #2	$156.73	10.546%	$173.2587	$173.26	$173.25	$173.30
Purchase #3	$48.54	12.290%	$54.5056	$54.51	$54.50	$54.50
Purchase #4	$250.36	4.185%	$260.8376	$260.84	$260.85	$260.80
Purchase #5	$134.78	7.682%	$145.1338	$145.13	$145.15	$145.10
Purchase #6	$57.75	3.563%	$59.8076	$59.81	$59.80	$59.80
Purchase #7	$132.78	6.300%	$141.1451	$141.15	$141.15	$141.10
7 purchase totals =	$956.56		$1,029.2121	$1,029.22	$1,029.20	$1,029.10