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	$47.79	5.709%	$50.5183	$50.52	$50.50	$50.50
Purchase #2	$120.96	8.616%	$131.3819	$131.38	$131.40	$131.40
Purchase #3	$30.41	10.868%	$33.715	$33.72	$33.70	$33.70
Purchase #4	$182.99	6.745%	$195.3327	$195.33	$195.35	$195.30
Purchase #5	$68.86	13.641%	$78.2532	$78.25	$78.25	$78.30
Purchase #6	$116.87	8.295%	$126.5644	$126.56	$126.55	$126.60
Purchase #7	$130.57	4.790%	$136.8243	$136.82	$136.80	$136.80
7 purchase totals =	$698.45		$752.5898	$752.58	$752.55	$752.60