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	$157.37	13.700%	$178.9297	$178.93	$178.95	$178.90
Purchase #2	$102.31	9.699%	$112.233	$112.23	$112.25	$112.20
Purchase #3	$85.71	9.190%	$93.5867	$93.59	$93.60	$93.60
Purchase #4	$203.76	7.406%	$218.8505	$218.85	$218.85	$218.90
Purchase #5	$198.37	11.749%	$221.6765	$221.68	$221.70	$221.70
Purchase #6	$89.82	13.440%	$101.8918	$101.89	$101.90	$101.90
Purchase #7	$104.56	13.682%	$118.8659	$118.87	$118.85	$118.90
7 purchase totals =	$941.90		$1,046.0341	$1,046.04	$1,046.10	$1,046.10