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	$112.99	12.515%	$127.1307	$127.13	$127.15	$127.10
Purchase #2	$38.51	12.737%	$43.415	$43.42	$43.40	$43.40
Purchase #3	$149.38	10.244%	$164.6825	$164.68	$164.70	$164.70
Purchase #4	$225.89	6.168%	$239.8229	$239.82	$239.80	$239.80
Purchase #5	$29.88	12.115%	$33.5	$33.50	$33.50	$33.50
Purchase #6	$242.59	11.631%	$270.8056	$270.81	$270.80	$270.80
Purchase #7	$183.90	13.847%	$209.3646	$209.36	$209.35	$209.40
7 purchase totals =	$983.14		$1,088.7213	$1,088.72	$1,088.70	$1,088.70