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	$173.36	6.414%	$184.4793	$184.48	$184.50	$184.50
Purchase #2	$139.91	12.731%	$157.7219	$157.72	$157.70	$157.70
Purchase #3	$185.57	12.386%	$208.5547	$208.55	$208.55	$208.60
Purchase #4	$78.96	4.542%	$82.5464	$82.55	$82.55	$82.50
Purchase #5	$182.88	11.687%	$204.2532	$204.25	$204.25	$204.30
Purchase #6	$31.53	5.652%	$33.3121	$33.31	$33.30	$33.30
Purchase #7	$159.86	13.315%	$181.1454	$181.15	$181.15	$181.10
7 purchase totals =	$952.07		$1,052.0130	$1,052.01	$1,052.00	$1,052.00