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	$178.45	6.209%	$189.53	$189.53	$189.55	$189.50
Purchase #2	$68.79	4.790%	$72.085	$72.09	$72.10	$72.10
Purchase #3	$89.33	10.674%	$98.8651	$98.87	$98.85	$98.90
Purchase #4	$186.38	11.752%	$208.2834	$208.28	$208.30	$208.30
Purchase #5	$69.68	11.831%	$77.9238	$77.92	$77.90	$77.90
Purchase #6	$73.82	12.756%	$83.2365	$83.24	$83.25	$83.20
Purchase #7	$224.57	9.269%	$245.3854	$245.39	$245.40	$245.40
7 purchase totals =	$891.02		$975.3092	$975.32	$975.35	$975.30