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	$201.88	10.111%	$222.2921	$222.29	$222.30	$222.30
Purchase #2	$219.79	11.709%	$245.5252	$245.53	$245.55	$245.50
Purchase #3	$175.32	4.664%	$183.4969	$183.50	$183.50	$183.50
Purchase #4	$241.62	11.553%	$269.5344	$269.53	$269.55	$269.50
Purchase #5	$206.79	3.864%	$214.7804	$214.78	$214.80	$214.80
Purchase #6	$67.55	12.748%	$76.1613	$76.16	$76.15	$76.20
Purchase #7	$78.48	5.584%	$82.8623	$82.86	$82.85	$82.90
7 purchase totals =	$1,191.43		$1,294.6526	$1,294.65	$1,294.70	$1,294.70