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	$61.59	5.270%	$64.8358	$64.84	$64.85	$64.80
Purchase #2	$63.76	12.738%	$71.8817	$71.88	$71.90	$71.90
Purchase #3	$112.63	9.572%	$123.4109	$123.41	$123.40	$123.40
Purchase #4	$18.59	5.143%	$19.5461	$19.55	$19.55	$19.50
Purchase #5	$56.37	5.440%	$59.4365	$59.44	$59.45	$59.40
Purchase #6	$210.33	3.593%	$217.8872	$217.89	$217.90	$217.90
Purchase #7	$230.96	11.386%	$257.2571	$257.26	$257.25	$257.30
7 purchase totals =	$754.23		$814.2553	$814.27	$814.30	$814.20