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	$245.97	8.173%	$266.0731	$266.07	$266.05	$266.10
Purchase #2	$134.29	13.623%	$152.5843	$152.58	$152.60	$152.60
Purchase #3	$86.54	12.529%	$97.3826	$97.38	$97.40	$97.40
Purchase #4	$231.64	10.140%	$255.1283	$255.13	$255.15	$255.10
Purchase #5	$173.54	4.230%	$180.8807	$180.88	$180.90	$180.90
Purchase #6	$38.54	12.840%	$43.4885	$43.49	$43.50	$43.50
Purchase #7	$88.68	9.395%	$97.0115	$97.01	$97.00	$97.00
7 purchase totals =	$999.20		$1,092.5490	$1,092.54	$1,092.60	$1,092.60