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	$96.60	9.163%	$105.4515	$105.45	$105.45	$105.50
Purchase #2	$85.45	10.116%	$94.0941	$94.09	$94.10	$94.10
Purchase #3	$75.50	10.410%	$83.3596	$83.36	$83.35	$83.40
Purchase #4	$179.80	3.389%	$185.8934	$185.89	$185.90	$185.90
Purchase #5	$80.76	5.508%	$85.2083	$85.21	$85.20	$85.20
Purchase #6	$249.39	11.295%	$277.5586	$277.56	$277.55	$277.60
Purchase #7	$14.73	5.494%	$15.5393	$15.54	$15.55	$15.50
7 purchase totals =	$782.23		$847.1048	$847.10	$847.10	$847.20