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	$26.82	7.596%	$28.8572	$28.86	$28.85	$28.90
Purchase #2	$209.85	7.667%	$225.9392	$225.94	$225.95	$225.90
Purchase #3	$116.36	12.235%	$130.5966	$130.60	$130.60	$130.60
Purchase #4	$228.27	13.400%	$258.8582	$258.86	$258.85	$258.90
Purchase #5	$170.89	5.377%	$180.0788	$180.08	$180.10	$180.10
Purchase #6	$52.70	13.509%	$59.8192	$59.82	$59.80	$59.80
Purchase #7	$125.61	13.347%	$142.3752	$142.38	$142.40	$142.40
7 purchase totals =	$930.50		$1,026.5244	$1,026.54	$1,026.55	$1,026.60