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	$20.73	7.589%	$22.3032	$22.30	$22.30	$22.30
Purchase #2	$92.44	9.118%	$100.8687	$100.87	$100.85	$100.90
Purchase #3	$69.93	11.473%	$77.9531	$77.95	$77.95	$78.00
Purchase #4	$76.27	8.135%	$82.4746	$82.47	$82.45	$82.50
Purchase #5	$96.45	9.502%	$105.6147	$105.61	$105.60	$105.60
Purchase #6	$78.86	8.122%	$85.265	$85.27	$85.25	$85.30
Purchase #7	$135.99	12.570%	$153.0839	$153.08	$153.10	$153.10
7 purchase totals =	$570.67		$627.5632	$627.55	$627.50	$627.70