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	$44.39	5.685%	$46.9136	$46.91	$46.90	$46.90
Purchase #2	$240.53	11.629%	$268.5012	$268.50	$268.50	$268.50
Purchase #3	$159.29	4.584%	$166.5919	$166.59	$166.60	$166.60
Purchase #4	$20.30	7.787%	$21.8808	$21.88	$21.90	$21.90
Purchase #5	$103.93	10.468%	$114.8094	$114.81	$114.80	$114.80
Purchase #6	$127.47	10.294%	$140.5918	$140.59	$140.60	$140.60
Purchase #7	$34.68	5.428%	$36.5624	$36.56	$36.55	$36.60
7 purchase totals =	$730.59		$795.8511	$795.84	$795.85	$795.90