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	$195.60	13.425%	$221.8593	$221.86	$221.85	$221.90
Purchase #2	$51.32	13.582%	$58.2903	$58.29	$58.30	$58.30
Purchase #3	$142.57	5.503%	$150.4156	$150.42	$150.40	$150.40
Purchase #4	$88.28	11.443%	$98.3819	$98.38	$98.40	$98.40
Purchase #5	$202.47	12.584%	$227.9488	$227.95	$227.95	$227.90
Purchase #6	$41.53	9.737%	$45.5738	$45.57	$45.55	$45.60
Purchase #7	$162.96	10.360%	$179.8427	$179.84	$179.85	$179.80
7 purchase totals =	$884.73		$982.3124	$982.31	$982.30	$982.30