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	$232.78	4.213%	$242.587	$242.59	$242.60	$242.60
Purchase #2	$183.60	13.541%	$208.4613	$208.46	$208.45	$208.50
Purchase #3	$31.45	5.688%	$33.2389	$33.24	$33.25	$33.20
Purchase #4	$153.42	13.607%	$174.2959	$174.30	$174.30	$174.30
Purchase #5	$247.70	3.515%	$256.4067	$256.41	$256.40	$256.40
Purchase #6	$162.65	7.175%	$174.3201	$174.32	$174.30	$174.30
Purchase #7	$11.53	3.279%	$11.9081	$11.91	$11.90	$11.90
7 purchase totals =	$1,023.13		$1,101.2180	$1,101.23	$1,101.20	$1,101.20