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	$91.79	13.114%	$103.8273	$103.83	$103.85	$103.80
Purchase #2	$238.77	12.616%	$268.8932	$268.89	$268.90	$268.90
Purchase #3	$9.43	4.584%	$9.8623	$9.86	$9.85	$9.90
Purchase #4	$166.62	13.121%	$188.4822	$188.48	$188.50	$188.50
Purchase #5	$191.69	4.422%	$200.1665	$200.17	$200.15	$200.20
Purchase #6	$104.76	4.705%	$109.689	$109.69	$109.70	$109.70
Purchase #7	$69.74	11.857%	$78.0091	$78.01	$78.00	$78.00
7 purchase totals =	$872.80		$958.9296	$958.93	$958.95	$959.00