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	$236.45	12.324%	$265.5901	$265.59	$265.60	$265.60
Purchase #2	$119.53	6.751%	$127.5995	$127.60	$127.60	$127.60
Purchase #3	$48.44	12.228%	$54.3632	$54.36	$54.35	$54.40
Purchase #4	$208.76	10.303%	$230.2685	$230.27	$230.25	$230.30
Purchase #5	$227.53	3.220%	$234.8565	$234.86	$234.85	$234.90
Purchase #6	$162.36	9.362%	$177.5601	$177.56	$177.55	$177.60
Purchase #7	$69.79	12.421%	$78.4586	$78.46	$78.45	$78.50
7 purchase totals =	$1,072.86		$1,168.6965	$1,168.70	$1,168.65	$1,168.90