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	$82.60	3.134%	$85.1887	$85.19	$85.20	$85.20
Purchase #2	$236.83	13.752%	$269.3989	$269.40	$269.40	$269.40
Purchase #3	$182.58	13.125%	$206.5436	$206.54	$206.55	$206.50
Purchase #4	$76.74	7.482%	$82.4817	$82.48	$82.50	$82.50
Purchase #5	$138.49	6.426%	$147.3894	$147.39	$147.40	$147.40
Purchase #6	$194.44	5.346%	$204.8348	$204.83	$204.85	$204.80
Purchase #7	$123.31	6.747%	$131.6297	$131.63	$131.65	$131.60
7 purchase totals =	$1,034.99		$1,127.4668	$1,127.46	$1,127.55	$1,127.40