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	$142.76	7.277%	$153.1486	$153.15	$153.15	$153.10
Purchase #2	$216.78	3.454%	$224.2676	$224.27	$224.25	$224.30
Purchase #3	$46.92	6.783%	$50.1026	$50.10	$50.10	$50.10
Purchase #4	$117.25	11.616%	$130.8698	$130.87	$130.85	$130.90
Purchase #5	$57.76	12.704%	$65.0978	$65.10	$65.10	$65.10
Purchase #6	$211.86	7.265%	$227.2516	$227.25	$227.25	$227.30
Purchase #7	$127.82	12.501%	$143.7988	$143.80	$143.80	$143.80
7 purchase totals =	$921.15		$994.5368	$994.54	$994.50	$994.60