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	$205.89	7.787%	$221.9227	$221.92	$221.90	$221.90
Purchase #2	$185.58	12.550%	$208.8703	$208.87	$208.85	$208.90
Purchase #3	$19.28	11.621%	$21.5205	$21.52	$21.50	$21.50
Purchase #4	$77.93	5.275%	$82.0408	$82.04	$82.05	$82.00
Purchase #5	$126.87	12.419%	$142.626	$142.63	$142.65	$142.60
Purchase #6	$31.54	4.661%	$33.0101	$33.01	$33.00	$33.00
Purchase #7	$54.91	4.313%	$57.2783	$57.28	$57.30	$57.30
7 purchase totals =	$702.00		$767.2687	$767.27	$767.25	$767.20