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	$226.61	7.129%	$242.765	$242.77	$242.75	$242.80
Purchase #2	$183.50	13.498%	$208.2688	$208.27	$208.25	$208.30
Purchase #3	$208.79	3.181%	$215.4316	$215.43	$215.45	$215.40
Purchase #4	$160.29	6.785%	$171.1657	$171.17	$171.15	$171.20
Purchase #5	$95.92	7.537%	$103.1495	$103.15	$103.15	$103.10
Purchase #6	$105.55	4.136%	$109.9155	$109.92	$109.90	$109.90
Purchase #7	$13.99	3.471%	$14.4756	$14.48	$14.50	$14.50
7 purchase totals =	$994.65		$1,065.1717	$1,065.19	$1,065.15	$1,065.20