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	$200.78	4.499%	$209.8131	$209.81	$209.80	$209.80
Purchase #2	$92.59	10.843%	$102.6295	$102.63	$102.65	$102.60
Purchase #3	$26.88	7.380%	$28.8637	$28.86	$28.85	$28.90
Purchase #4	$113.27	12.489%	$127.4163	$127.42	$127.40	$127.40
Purchase #5	$95.54	10.162%	$105.2488	$105.25	$105.25	$105.20
Purchase #6	$214.30	9.440%	$234.5299	$234.53	$234.55	$234.50
Purchase #7	$131.39	7.787%	$141.6213	$141.62	$141.60	$141.60
7 purchase totals =	$874.75		$950.1226	$950.12	$950.10	$950.00