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	$193.98	11.498%	$216.2838	$216.28	$216.30	$216.30
Purchase #2	$103.51	12.801%	$116.7603	$116.76	$116.75	$116.80
Purchase #3	$125.36	13.327%	$142.0667	$142.07	$142.05	$142.10
Purchase #4	$181.88	5.510%	$191.9016	$191.90	$191.90	$191.90
Purchase #5	$117.72	5.310%	$123.9709	$123.97	$123.95	$124.00
Purchase #6	$98.65	10.564%	$109.0714	$109.07	$109.05	$109.10
Purchase #7	$56.56	13.477%	$64.1826	$64.18	$64.20	$64.20
7 purchase totals =	$877.66		$964.2373	$964.23	$964.20	$964.40