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	$112.77	5.312%	$118.7603	$118.76	$118.75	$118.80
Purchase #2	$135.73	10.791%	$150.3766	$150.38	$150.40	$150.40
Purchase #3	$148.89	4.716%	$155.9117	$155.91	$155.90	$155.90
Purchase #4	$79.41	13.750%	$90.3289	$90.33	$90.35	$90.30
Purchase #5	$102.69	6.702%	$109.5723	$109.57	$109.55	$109.60
Purchase #6	$127.91	13.692%	$145.4234	$145.42	$145.40	$145.40
Purchase #7	$153.46	6.147%	$162.8932	$162.89	$162.90	$162.90
7 purchase totals =	$860.86		$933.2664	$933.26	$933.25	$933.30