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	$89.57	5.515%	$94.5098	$94.51	$94.50	$94.50
Purchase #2	$44.83	5.450%	$47.2732	$47.27	$47.25	$47.30
Purchase #3	$168.29	9.367%	$184.0537	$184.05	$184.05	$184.10
Purchase #4	$170.38	11.303%	$189.6381	$189.64	$189.65	$189.60
Purchase #5	$99.87	8.611%	$108.4698	$108.47	$108.45	$108.50
Purchase #6	$105.72	5.129%	$111.1424	$111.14	$111.15	$111.10
Purchase #7	$6.62	7.177%	$7.0951	$7.10	$7.10	$7.10
7 purchase totals =	$685.28		$742.1821	$742.18	$742.15	$742.20