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	$142.66	4.499%	$149.0783	$149.08	$149.10	$149.10
Purchase #2	$106.81	12.188%	$119.828	$119.83	$119.85	$119.80
Purchase #3	$187.42	8.559%	$203.4613	$203.46	$203.45	$203.50
Purchase #4	$43.77	4.788%	$45.8657	$45.87	$45.85	$45.90
Purchase #5	$94.59	8.865%	$102.9754	$102.98	$103.00	$103.00
Purchase #6	$226.69	12.452%	$254.9174	$254.92	$254.90	$254.90
Purchase #7	$115.81	10.419%	$127.8762	$127.88	$127.90	$127.90
7 purchase totals =	$917.75		$1,004.0023	$1,004.02	$1,004.05	$1,004.10