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	$220.32	11.378%	$245.388	$245.39	$245.40	$245.40
Purchase #2	$28.31	12.668%	$31.8963	$31.90	$31.90	$31.90
Purchase #3	$242.63	10.257%	$267.5166	$267.52	$267.50	$267.50
Purchase #4	$79.40	4.771%	$83.1882	$83.19	$83.20	$83.20
Purchase #5	$37.48	4.506%	$39.1688	$39.17	$39.15	$39.20
Purchase #6	$135.82	12.239%	$152.443	$152.44	$152.45	$152.40
Purchase #7	$114.76	7.653%	$123.5426	$123.54	$123.55	$123.50
7 purchase totals =	$858.72		$943.1435	$943.15	$943.15	$943.10