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	$170.54	4.736%	$178.6168	$178.62	$178.60	$178.60
Purchase #2	$100.85	8.134%	$109.0531	$109.05	$109.05	$109.10
Purchase #3	$7.35	3.275%	$7.5907	$7.59	$7.60	$7.60
Purchase #4	$62.27	6.754%	$66.4757	$66.48	$66.50	$66.50
Purchase #5	$154.40	5.139%	$162.3346	$162.33	$162.35	$162.30
Purchase #6	$39.27	9.797%	$43.1173	$43.12	$43.10	$43.10
Purchase #7	$30.66	4.190%	$31.9447	$31.94	$31.95	$31.90
7 purchase totals =	$565.34		$599.1329	$599.13	$599.15	$599.10