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	$54.96	8.618%	$59.6965	$59.70	$59.70	$59.70
Purchase #2	$248.79	13.153%	$281.5133	$281.51	$281.50	$281.50
Purchase #3	$165.64	5.834%	$175.3034	$175.30	$175.30	$175.30
Purchase #4	$111.89	13.372%	$126.8519	$126.85	$126.85	$126.90
Purchase #5	$67.37	6.789%	$71.9437	$71.94	$71.95	$71.90
Purchase #6	$170.50	13.693%	$193.8466	$193.85	$193.85	$193.80
Purchase #7	$210.89	6.479%	$224.5536	$224.55	$224.55	$224.60
7 purchase totals =	$1,030.04		$1,133.7090	$1,133.70	$1,133.70	$1,133.70