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	$118.59	10.158%	$130.6364	$130.64	$130.65	$130.60
Purchase #2	$242.99	3.615%	$251.7741	$251.77	$251.75	$251.80
Purchase #3	$243.64	6.518%	$259.5205	$259.52	$259.50	$259.50
Purchase #4	$124.89	5.385%	$131.6153	$131.62	$131.60	$131.60
Purchase #5	$47.86	4.121%	$49.8323	$49.83	$49.85	$49.80
Purchase #6	$82.82	4.708%	$86.7192	$86.72	$86.70	$86.70
Purchase #7	$233.29	5.404%	$245.897	$245.90	$245.90	$245.90
7 purchase totals =	$1,094.08		$1,155.9948	$1,156.00	$1,155.95	$1,155.90