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	$195.28	10.542%	$215.8664	$215.87	$215.85	$215.90
Purchase #2	$103.83	7.636%	$111.7585	$111.76	$111.75	$111.80
Purchase #3	$95.97	9.289%	$104.8847	$104.88	$104.90	$104.90
Purchase #4	$116.43	3.354%	$120.3351	$120.34	$120.35	$120.30
Purchase #5	$245.88	11.759%	$274.793	$274.79	$274.80	$274.80
Purchase #6	$151.46	10.845%	$167.8858	$167.89	$167.90	$167.90
Purchase #7	$179.40	10.774%	$198.7286	$198.73	$198.75	$198.70
7 purchase totals =	$1,088.25		$1,194.2521	$1,194.26	$1,194.30	$1,194.30