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	$203.95	9.648%	$223.6271	$223.63	$223.65	$223.60
Purchase #2	$28.49	10.627%	$31.5176	$31.52	$31.50	$31.50
Purchase #3	$80.29	7.415%	$86.2435	$86.24	$86.25	$86.20
Purchase #4	$138.93	13.857%	$158.1815	$158.18	$158.20	$158.20
Purchase #5	$55.78	9.711%	$61.1968	$61.20	$61.20	$61.20
Purchase #6	$90.52	5.451%	$95.4542	$95.45	$95.45	$95.50
Purchase #7	$173.84	12.113%	$194.8972	$194.90	$194.90	$194.90
7 purchase totals =	$771.80		$851.1179	$851.12	$851.15	$851.10