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	$225.86	5.582%	$238.4675	$238.47	$238.45	$238.50
Purchase #2	$35.78	6.741%	$38.1919	$38.19	$38.20	$38.20
Purchase #3	$154.53	13.596%	$175.5399	$175.54	$175.55	$175.50
Purchase #4	$194.41	9.393%	$212.6709	$212.67	$212.65	$212.70
Purchase #5	$204.78	13.818%	$233.0765	$233.08	$233.10	$233.10
Purchase #6	$101.66	3.800%	$105.5231	$105.52	$105.50	$105.50
Purchase #7	$102.37	12.691%	$115.3618	$115.36	$115.35	$115.40
7 purchase totals =	$1,019.39		$1,118.8316	$1,118.83	$1,118.80	$1,118.90