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	$138.73	12.226%	$155.6911	$155.69	$155.70	$155.70
Purchase #2	$184.41	4.813%	$193.2857	$193.29	$193.30	$193.30
Purchase #3	$16.94	8.259%	$18.3391	$18.34	$18.35	$18.30
Purchase #4	$213.93	4.597%	$223.7644	$223.76	$223.75	$223.80
Purchase #5	$52.53	12.844%	$59.277	$59.28	$59.30	$59.30
Purchase #6	$154.94	3.467%	$160.3118	$160.31	$160.30	$160.30
Purchase #7	$225.28	13.245%	$255.1183	$255.12	$255.10	$255.10
7 purchase totals =	$986.76		$1,065.7874	$1,065.79	$1,065.80	$1,065.80