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	$94.49	12.227%	$106.0433	$106.04	$106.05	$106.00
Purchase #2	$32.74	9.279%	$35.7779	$35.78	$35.80	$35.80
Purchase #3	$103.98	11.509%	$115.9471	$115.95	$115.95	$115.90
Purchase #4	$212.78	4.793%	$222.9785	$222.98	$223.00	$223.00
Purchase #5	$158.55	13.449%	$179.8734	$179.87	$179.85	$179.90
Purchase #6	$55.53	6.529%	$59.1556	$59.16	$59.15	$59.20
Purchase #7	$100.83	11.716%	$112.6432	$112.64	$112.65	$112.60
7 purchase totals =	$758.90		$832.4190	$832.42	$832.45	$832.40