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	$47.59	9.821%	$52.2638	$52.26	$52.25	$52.30
Purchase #2	$232.50	7.463%	$249.8515	$249.85	$249.85	$249.90
Purchase #3	$114.42	3.745%	$118.705	$118.71	$118.70	$118.70
Purchase #4	$35.34	5.320%	$37.2201	$37.22	$37.20	$37.20
Purchase #5	$103.35	5.311%	$108.8389	$108.84	$108.85	$108.80
Purchase #6	$75.39	3.846%	$78.2895	$78.29	$78.30	$78.30
Purchase #7	$78.79	3.447%	$81.5059	$81.51	$81.50	$81.50
7 purchase totals =	$687.38		$726.6747	$726.68	$726.65	$726.70