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	$112.89	4.735%	$118.2353	$118.24	$118.25	$118.20
Purchase #2	$213.43	11.651%	$238.2967	$238.30	$238.30	$238.30
Purchase #3	$247.91	8.506%	$268.9972	$269.00	$269.00	$269.00
Purchase #4	$17.27	13.179%	$19.546	$19.55	$19.55	$19.50
Purchase #5	$95.97	13.748%	$109.164	$109.16	$109.15	$109.20
Purchase #6	$64.51	12.616%	$72.6486	$72.65	$72.65	$72.60
Purchase #7	$126.33	3.296%	$130.4938	$130.49	$130.50	$130.50
7 purchase totals =	$878.31		$957.3816	$957.39	$957.40	$957.30