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	$222.88	4.722%	$233.4044	$233.40	$233.40	$233.40
Purchase #2	$238.62	7.304%	$256.0488	$256.05	$256.05	$256.00
Purchase #3	$83.78	10.585%	$92.6481	$92.65	$92.65	$92.60
Purchase #4	$46.64	13.450%	$52.9131	$52.91	$52.90	$52.90
Purchase #5	$227.62	3.803%	$236.2764	$236.28	$236.30	$236.30
Purchase #6	$83.52	8.522%	$90.6376	$90.64	$90.65	$90.60
Purchase #7	$219.37	11.627%	$244.8761	$244.88	$244.90	$244.90
7 purchase totals =	$1,122.43		$1,206.8045	$1,206.81	$1,206.85	$1,206.70