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	$94.40	6.376%	$100.4189	$100.42	$100.40	$100.40
Purchase #2	$99.73	6.758%	$106.4698	$106.47	$106.45	$106.50
Purchase #3	$155.45	8.279%	$168.3197	$168.32	$168.30	$168.30
Purchase #4	$239.30	3.298%	$247.1921	$247.19	$247.20	$247.20
Purchase #5	$33.93	9.861%	$37.2758	$37.28	$37.30	$37.30
Purchase #6	$225.29	8.646%	$244.7686	$244.77	$244.75	$244.80
Purchase #7	$116.27	13.421%	$131.8746	$131.87	$131.85	$131.90
7 purchase totals =	$964.37		$1,036.3195	$1,036.32	$1,036.25	$1,036.40