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	$82.55	3.294%	$85.2692	$85.27	$85.25	$85.30
Purchase #2	$45.33	11.615%	$50.5951	$50.60	$50.60	$50.60
Purchase #3	$176.95	11.521%	$197.3364	$197.34	$197.35	$197.30
Purchase #4	$123.86	10.316%	$136.6374	$136.64	$136.65	$136.60
Purchase #5	$222.99	12.393%	$250.6252	$250.63	$250.65	$250.60
Purchase #6	$192.33	10.226%	$211.9977	$212.00	$212.00	$212.00
Purchase #7	$64.37	11.250%	$71.6116	$71.61	$71.60	$71.60
7 purchase totals =	$908.38		$1,004.0726	$1,004.09	$1,004.10	$1,004.00