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	$127.25	11.800%	$142.2655	$142.27	$142.25	$142.30
Purchase #2	$175.87	9.476%	$192.5354	$192.54	$192.55	$192.50
Purchase #3	$19.77	5.674%	$20.8917	$20.89	$20.90	$20.90
Purchase #4	$114.89	5.514%	$121.225	$121.23	$121.25	$121.20
Purchase #5	$136.79	10.196%	$150.7371	$150.74	$150.75	$150.70
Purchase #6	$238.78	12.529%	$268.6967	$268.70	$268.70	$268.70
Purchase #7	$141.97	3.175%	$146.4775	$146.48	$146.50	$146.50
7 purchase totals =	$955.32		$1,042.8289	$1,042.85	$1,042.90	$1,042.80