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	$176.38	7.781%	$190.1041	$190.10	$190.10	$190.10
Purchase #2	$66.90	11.326%	$74.4771	$74.48	$74.50	$74.50
Purchase #3	$195.76	13.408%	$222.0075	$222.01	$222.00	$222.00
Purchase #4	$130.97	8.425%	$142.0042	$142.00	$142.00	$142.00
Purchase #5	$42.74	13.299%	$48.424	$48.42	$48.40	$48.40
Purchase #6	$30.34	11.215%	$33.7426	$33.74	$33.75	$33.70
Purchase #7	$118.69	7.324%	$127.3829	$127.38	$127.40	$127.40
7 purchase totals =	$761.78		$838.1424	$838.13	$838.15	$838.10