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	$153.68	12.236%	$172.4843	$172.48	$172.50	$172.50
Purchase #2	$229.85	11.649%	$256.6252	$256.63	$256.65	$256.60
Purchase #3	$119.61	3.470%	$123.7605	$123.76	$123.75	$123.80
Purchase #4	$17.28	10.216%	$19.0453	$19.05	$19.05	$19.00
Purchase #5	$187.85	4.109%	$195.5688	$195.57	$195.55	$195.60
Purchase #6	$163.88	13.185%	$185.4876	$185.49	$185.50	$185.50
Purchase #7	$155.42	9.844%	$170.7195	$170.72	$170.70	$170.70
7 purchase totals =	$1,027.57		$1,123.6912	$1,123.70	$1,123.70	$1,123.70