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	$114.26	11.393%	$127.2776	$127.28	$127.30	$127.30
Purchase #2	$5.35	3.588%	$5.542	$5.54	$5.55	$5.50
Purchase #3	$97.64	4.583%	$102.1148	$102.11	$102.10	$102.10
Purchase #4	$125.36	9.799%	$137.644	$137.64	$137.65	$137.60
Purchase #5	$5.26	5.717%	$5.5607	$5.56	$5.55	$5.60
Purchase #6	$27.48	3.777%	$28.5179	$28.52	$28.50	$28.50
Purchase #7	$123.27	3.449%	$127.5216	$127.52	$127.50	$127.50
7 purchase totals =	$498.62		$534.1786	$534.17	$534.15	$534.10