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	$23.32	5.652%	$24.638	$24.64	$24.65	$24.60
Purchase #2	$162.85	12.741%	$183.5987	$183.60	$183.60	$183.60
Purchase #3	$178.33	5.634%	$188.3771	$188.38	$188.40	$188.40
Purchase #4	$200.86	5.617%	$212.1423	$212.14	$212.15	$212.10
Purchase #5	$189.65	4.845%	$198.8385	$198.84	$198.85	$198.80
Purchase #6	$164.89	4.752%	$172.7256	$172.73	$172.75	$172.70
Purchase #7	$72.75	12.776%	$82.0445	$82.04	$82.05	$82.00
7 purchase totals =	$992.65		$1,062.3647	$1,062.37	$1,062.45	$1,062.20