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	$232.44	13.628%	$264.1169	$264.12	$264.10	$264.10
Purchase #2	$55.41	8.257%	$59.9852	$59.99	$60.00	$60.00
Purchase #3	$137.27	8.386%	$148.7815	$148.78	$148.80	$148.80
Purchase #4	$214.69	8.802%	$233.587	$233.59	$233.60	$233.60
Purchase #5	$78.68	9.175%	$85.8989	$85.90	$85.90	$85.90
Purchase #6	$150.45	9.371%	$164.5487	$164.55	$164.55	$164.50
Purchase #7	$136.33	8.839%	$148.3802	$148.38	$148.40	$148.40
7 purchase totals =	$1,005.27		$1,105.2984	$1,105.31	$1,105.35	$1,105.30