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	$95.27	7.718%	$102.6229	$102.62	$102.60	$102.60
Purchase #2	$113.89	12.323%	$127.9247	$127.92	$127.90	$127.90
Purchase #3	$89.85	10.304%	$99.1081	$99.11	$99.10	$99.10
Purchase #4	$210.92	6.187%	$223.9696	$223.97	$223.95	$224.00
Purchase #5	$134.70	8.752%	$146.4889	$146.49	$146.50	$146.50
Purchase #6	$149.68	5.542%	$157.9753	$157.98	$158.00	$158.00
Purchase #7	$57.27	12.449%	$64.3995	$64.40	$64.40	$64.40
7 purchase totals =	$851.58		$922.4890	$922.49	$922.45	$922.50