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	$207.90	9.449%	$227.5445	$227.54	$227.55	$227.50
Purchase #2	$242.25	3.712%	$251.2423	$251.24	$251.25	$251.20
Purchase #3	$170.45	9.778%	$187.1166	$187.12	$187.10	$187.10
Purchase #4	$46.72	9.328%	$51.078	$51.08	$51.10	$51.10
Purchase #5	$240.37	9.742%	$263.7868	$263.79	$263.80	$263.80
Purchase #6	$42.59	8.793%	$46.3349	$46.33	$46.35	$46.30
Purchase #7	$180.96	8.598%	$196.5189	$196.52	$196.50	$196.50
7 purchase totals =	$1,131.24		$1,223.6220	$1,223.62	$1,223.65	$1,223.50