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	$32.65	11.660%	$36.457	$36.46	$36.45	$36.50
Purchase #2	$33.97	10.730%	$37.615	$37.62	$37.60	$37.60
Purchase #3	$166.30	5.450%	$175.3634	$175.36	$175.35	$175.40
Purchase #4	$39.81	6.563%	$42.4227	$42.42	$42.40	$42.40
Purchase #5	$245.69	4.154%	$255.896	$255.90	$255.90	$255.90
Purchase #6	$146.78	10.579%	$162.3079	$162.31	$162.30	$162.30
Purchase #7	$101.97	6.165%	$108.2565	$108.26	$108.25	$108.30
7 purchase totals =	$767.17		$818.3185	$818.33	$818.25	$818.40