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	$248.48	3.792%	$257.9024	$257.90	$257.90	$257.90
Purchase #2	$46.85	7.360%	$50.2982	$50.30	$50.30	$50.30
Purchase #3	$163.61	10.859%	$181.3764	$181.38	$181.40	$181.40
Purchase #4	$231.85	9.171%	$253.113	$253.11	$253.10	$253.10
Purchase #5	$159.88	3.798%	$165.9522	$165.95	$165.95	$166.00
Purchase #6	$31.32	6.289%	$33.2897	$33.29	$33.30	$33.30
Purchase #7	$112.66	6.477%	$119.957	$119.96	$119.95	$120.00
7 purchase totals =	$994.65		$1,061.8889	$1,061.89	$1,061.90	$1,062.00