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	$92.49	13.444%	$104.9244	$104.92	$104.90	$104.90
Purchase #2	$246.82	3.619%	$255.7524	$255.75	$255.75	$255.80
Purchase #3	$115.69	12.654%	$130.3294	$130.33	$130.35	$130.30
Purchase #4	$108.54	6.181%	$115.2489	$115.25	$115.25	$115.20
Purchase #5	$222.90	11.505%	$248.5446	$248.54	$248.55	$248.50
Purchase #6	$154.87	10.747%	$171.5139	$171.51	$171.50	$171.50
Purchase #7	$47.52	10.701%	$52.6051	$52.61	$52.60	$52.60
7 purchase totals =	$988.83		$1,078.9187	$1,078.91	$1,078.90	$1,078.80