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	$147.81	7.450%	$158.8218	$158.82	$158.80	$158.80
Purchase #2	$223.56	7.836%	$241.0782	$241.08	$241.10	$241.10
Purchase #3	$45.99	11.644%	$51.3451	$51.35	$51.35	$51.30
Purchase #4	$94.81	10.376%	$104.6475	$104.65	$104.65	$104.60
Purchase #5	$170.32	10.278%	$187.8255	$187.83	$187.85	$187.80
Purchase #6	$56.78	4.558%	$59.368	$59.37	$59.35	$59.40
Purchase #7	$99.95	6.874%	$106.8206	$106.82	$106.80	$106.80
7 purchase totals =	$839.22		$909.9067	$909.92	$909.90	$909.80