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	$232.38	8.185%	$251.4003	$251.40	$251.40	$251.40
Purchase #2	$41.88	4.537%	$43.7801	$43.78	$43.80	$43.80
Purchase #3	$72.54	9.544%	$79.4632	$79.46	$79.45	$79.50
Purchase #4	$35.86	8.138%	$38.7783	$38.78	$38.80	$38.80
Purchase #5	$47.69	9.395%	$52.1705	$52.17	$52.15	$52.20
Purchase #6	$113.64	8.706%	$123.5335	$123.53	$123.55	$123.50
Purchase #7	$196.97	9.386%	$215.4576	$215.46	$215.45	$215.50
7 purchase totals =	$740.96		$804.5835	$804.58	$804.60	$804.70