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	$53.80	13.174%	$60.8876	$60.89	$60.90	$60.90
Purchase #2	$50.53	3.177%	$52.1353	$52.14	$52.15	$52.10
Purchase #3	$64.50	3.752%	$66.92	$66.92	$66.90	$66.90
Purchase #4	$54.34	10.383%	$59.9821	$59.98	$60.00	$60.00
Purchase #5	$139.99	3.396%	$144.7441	$144.74	$144.75	$144.70
Purchase #6	$70.64	3.427%	$73.0608	$73.06	$73.05	$73.10
Purchase #7	$103.69	5.692%	$109.592	$109.59	$109.60	$109.60
7 purchase totals =	$537.49		$567.3219	$567.32	$567.35	$567.30