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	$178.98	9.744%	$196.4198	$196.42	$196.40	$196.40
Purchase #2	$15.34	3.179%	$15.8277	$15.83	$15.85	$15.80
Purchase #3	$98.25	8.456%	$106.558	$106.56	$106.55	$106.60
Purchase #4	$95.49	5.776%	$101.0055	$101.01	$101.00	$101.00
Purchase #5	$112.43	13.537%	$127.6496	$127.65	$127.65	$127.60
Purchase #6	$248.66	5.318%	$261.8837	$261.88	$261.90	$261.90
Purchase #7	$238.29	11.111%	$264.7664	$264.77	$264.75	$264.80
7 purchase totals =	$987.44		$1,074.1107	$1,074.12	$1,074.10	$1,074.10