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	$48.98	13.120%	$55.4062	$55.41	$55.40	$55.40
Purchase #2	$55.62	11.288%	$61.8984	$61.90	$61.90	$61.90
Purchase #3	$32.83	5.200%	$34.5372	$34.54	$34.55	$34.50
Purchase #4	$53.45	10.840%	$59.244	$59.24	$59.25	$59.20
Purchase #5	$83.96	10.570%	$92.8346	$92.83	$92.85	$92.80
Purchase #6	$211.35	10.553%	$233.6538	$233.65	$233.65	$233.70
Purchase #7	$225.45	7.570%	$242.5166	$242.52	$242.50	$242.50
7 purchase totals =	$711.64		$780.0908	$780.09	$780.10	$780.00