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	$27.91	5.295%	$29.3878	$29.39	$29.40	$29.40
Purchase #2	$150.63	13.790%	$171.4019	$171.40	$171.40	$171.40
Purchase #3	$183.77	12.196%	$206.1826	$206.18	$206.20	$206.20
Purchase #4	$56.38	9.750%	$61.8771	$61.88	$61.90	$61.90
Purchase #5	$141.36	3.547%	$146.374	$146.37	$146.35	$146.40
Purchase #6	$211.51	5.380%	$222.8892	$222.89	$222.90	$222.90
Purchase #7	$99.30	6.515%	$105.7694	$105.77	$105.75	$105.80
7 purchase totals =	$870.86		$943.8820	$943.88	$943.90	$944.00