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	$196.65	13.621%	$223.4357	$223.44	$223.45	$223.40
Purchase #2	$135.51	7.856%	$146.1557	$146.16	$146.15	$146.20
Purchase #3	$168.81	10.573%	$186.6583	$186.66	$186.65	$186.70
Purchase #4	$177.34	4.702%	$185.6785	$185.68	$185.70	$185.70
Purchase #5	$51.61	5.222%	$54.3051	$54.31	$54.30	$54.30
Purchase #6	$79.39	8.104%	$85.8238	$85.82	$85.80	$85.80
Purchase #7	$113.66	10.237%	$125.2954	$125.30	$125.30	$125.30
7 purchase totals =	$922.97		$1,007.3525	$1,007.37	$1,007.35	$1,007.40