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	$75.56	12.552%	$85.0443	$85.04	$85.05	$85.00
Purchase #2	$246.92	8.710%	$268.4267	$268.43	$268.45	$268.40
Purchase #3	$101.38	12.833%	$114.3901	$114.39	$114.40	$114.40
Purchase #4	$96.81	5.845%	$102.4685	$102.47	$102.45	$102.50
Purchase #5	$249.88	5.104%	$262.6339	$262.63	$262.65	$262.60
Purchase #6	$247.25	9.560%	$270.8871	$270.89	$270.90	$270.90
Purchase #7	$84.26	9.732%	$92.4602	$92.46	$92.45	$92.50
7 purchase totals =	$1,102.06		$1,196.3108	$1,196.31	$1,196.35	$1,196.30