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	$228.76	7.482%	$245.8758	$245.88	$245.90	$245.90
Purchase #2	$206.49	4.262%	$215.2906	$215.29	$215.30	$215.30
Purchase #3	$75.91	8.539%	$82.392	$82.39	$82.40	$82.40
Purchase #4	$203.28	12.423%	$228.5335	$228.53	$228.55	$228.50
Purchase #5	$101.25	10.584%	$111.9663	$111.97	$111.95	$112.00
Purchase #6	$29.34	12.364%	$32.9676	$32.97	$32.95	$33.00
Purchase #7	$19.30	11.380%	$21.4963	$21.50	$21.50	$21.50
7 purchase totals =	$864.33		$938.5221	$938.53	$938.55	$938.60