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	$208.57	10.219%	$229.8838	$229.88	$229.90	$229.90
Purchase #2	$96.94	3.566%	$100.3969	$100.40	$100.40	$100.40
Purchase #3	$30.76	9.583%	$33.7077	$33.71	$33.70	$33.70
Purchase #4	$233.70	9.620%	$256.1819	$256.18	$256.20	$256.20
Purchase #5	$166.76	9.465%	$182.5438	$182.54	$182.55	$182.50
Purchase #6	$167.68	13.583%	$190.456	$190.46	$190.45	$190.50
Purchase #7	$127.37	10.125%	$140.2662	$140.27	$140.25	$140.30
7 purchase totals =	$1,031.78		$1,133.4363	$1,133.44	$1,133.45	$1,133.50