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	$181.63	9.344%	$198.6015	$198.60	$198.60	$198.60
Purchase #2	$127.98	13.793%	$145.6323	$145.63	$145.65	$145.60
Purchase #3	$67.54	5.624%	$71.3384	$71.34	$71.35	$71.30
Purchase #4	$233.44	12.620%	$262.9001	$262.90	$262.90	$262.90
Purchase #5	$68.71	6.782%	$73.3699	$73.37	$73.35	$73.40
Purchase #6	$51.78	10.712%	$57.3267	$57.33	$57.35	$57.30
Purchase #7	$109.96	5.827%	$116.3674	$116.37	$116.35	$116.40
7 purchase totals =	$841.04		$925.5363	$925.54	$925.55	$925.50