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	$206.54	4.185%	$215.1837	$215.18	$215.20	$215.20
Purchase #2	$127.34	11.776%	$142.3356	$142.34	$142.35	$142.30
Purchase #3	$17.41	8.102%	$18.8206	$18.82	$18.80	$18.80
Purchase #4	$121.70	5.276%	$128.1209	$128.12	$128.10	$128.10
Purchase #5	$241.66	3.194%	$249.3786	$249.38	$249.40	$249.40
Purchase #6	$67.30	8.137%	$72.7762	$72.78	$72.80	$72.80
Purchase #7	$117.89	4.559%	$123.2646	$123.26	$123.25	$123.30
7 purchase totals =	$899.84		$949.8802	$949.88	$949.90	$949.90