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	$93.86	11.276%	$104.4437	$104.44	$104.45	$104.40
Purchase #2	$188.79	12.778%	$212.9136	$212.91	$212.90	$212.90
Purchase #3	$121.96	5.296%	$128.419	$128.42	$128.40	$128.40
Purchase #4	$149.43	7.660%	$160.8763	$160.88	$160.90	$160.90
Purchase #5	$72.41	11.394%	$80.6604	$80.66	$80.65	$80.70
Purchase #6	$72.28	9.807%	$79.3685	$79.37	$79.35	$79.40
Purchase #7	$183.42	7.188%	$196.6042	$196.60	$196.60	$196.60
7 purchase totals =	$882.15		$963.2857	$963.28	$963.25	$963.30