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	$134.86	8.454%	$146.2611	$146.26	$146.25	$146.30
Purchase #2	$93.88	12.440%	$105.5587	$105.56	$105.55	$105.60
Purchase #3	$134.47	3.647%	$139.3741	$139.37	$139.35	$139.40
Purchase #4	$119.44	10.782%	$132.318	$132.32	$132.30	$132.30
Purchase #5	$59.59	7.494%	$64.0557	$64.06	$64.05	$64.10
Purchase #6	$130.25	7.721%	$140.3066	$140.31	$140.30	$140.30
Purchase #7	$210.74	3.666%	$218.4657	$218.47	$218.45	$218.50
7 purchase totals =	$883.23		$946.3399	$946.35	$946.25	$946.50