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	$215.49	3.351%	$222.7111	$222.71	$222.70	$222.70
Purchase #2	$78.75	5.537%	$83.1104	$83.11	$83.10	$83.10
Purchase #3	$23.74	7.388%	$25.4939	$25.49	$25.50	$25.50
Purchase #4	$208.73	13.757%	$237.445	$237.45	$237.45	$237.40
Purchase #5	$154.85	5.213%	$162.9223	$162.92	$162.90	$162.90
Purchase #6	$138.92	4.835%	$145.6368	$145.64	$145.65	$145.60
Purchase #7	$196.79	11.304%	$219.0351	$219.04	$219.05	$219.00
7 purchase totals =	$1,017.27		$1,096.3546	$1,096.36	$1,096.35	$1,096.20