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	$159.46	10.412%	$176.063	$176.06	$176.05	$176.10
Purchase #2	$200.57	13.865%	$228.379	$228.38	$228.40	$228.40
Purchase #3	$76.58	7.811%	$82.5617	$82.56	$82.55	$82.60
Purchase #4	$187.49	10.114%	$206.4527	$206.45	$206.45	$206.50
Purchase #5	$145.51	11.620%	$162.4183	$162.42	$162.40	$162.40
Purchase #6	$130.90	8.116%	$141.5238	$141.52	$141.50	$141.50
Purchase #7	$111.69	3.660%	$115.7779	$115.78	$115.80	$115.80
7 purchase totals =	$1,012.20		$1,113.1764	$1,113.17	$1,113.15	$1,113.30