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	$47.59	6.347%	$50.6105	$50.61	$50.60	$50.60
Purchase #2	$95.80	10.873%	$106.2163	$106.22	$106.20	$106.20
Purchase #3	$37.57	12.813%	$42.3838	$42.38	$42.40	$42.40
Purchase #4	$241.44	12.157%	$270.7919	$270.79	$270.80	$270.80
Purchase #5	$184.39	6.277%	$195.9642	$195.96	$195.95	$196.00
Purchase #6	$146.28	5.206%	$153.8953	$153.90	$153.90	$153.90
Purchase #7	$169.37	7.726%	$182.4555	$182.46	$182.45	$182.50
7 purchase totals =	$922.44		$1,002.3175	$1,002.32	$1,002.30	$1,002.40