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	$122.58	7.603%	$131.8998	$131.90	$131.90	$131.90
Purchase #2	$207.71	11.323%	$231.229	$231.23	$231.25	$231.20
Purchase #3	$130.94	4.117%	$136.3308	$136.33	$136.35	$136.30
Purchase #4	$39.64	12.464%	$44.5807	$44.58	$44.60	$44.60
Purchase #5	$206.88	7.704%	$222.818	$222.82	$222.80	$222.80
Purchase #6	$202.90	8.723%	$220.599	$220.60	$220.60	$220.60
Purchase #7	$50.94	10.842%	$56.4629	$56.46	$56.45	$56.50
7 purchase totals =	$961.59		$1,043.9202	$1,043.92	$1,043.95	$1,043.90