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	$54.27	5.323%	$57.1588	$57.16	$57.15	$57.20
Purchase #2	$69.51	3.388%	$71.865	$71.87	$71.85	$71.90
Purchase #3	$59.26	4.247%	$61.7768	$61.78	$61.80	$61.80
Purchase #4	$161.65	3.636%	$167.5276	$167.53	$167.55	$167.50
Purchase #5	$45.51	10.494%	$50.2858	$50.29	$50.30	$50.30
Purchase #6	$196.71	11.340%	$219.0169	$219.02	$219.00	$219.00
Purchase #7	$228.88	8.796%	$249.0123	$249.01	$249.00	$249.00
7 purchase totals =	$815.79		$876.6432	$876.66	$876.65	$876.70