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	$190.88	4.476%	$199.4238	$199.42	$199.40	$199.40
Purchase #2	$127.40	13.646%	$144.785	$144.79	$144.80	$144.80
Purchase #3	$64.40	13.676%	$73.2073	$73.21	$73.20	$73.20
Purchase #4	$134.32	13.443%	$152.3766	$152.38	$152.40	$152.40
Purchase #5	$80.61	11.818%	$90.1365	$90.14	$90.15	$90.10
Purchase #6	$132.38	6.586%	$141.0985	$141.10	$141.10	$141.10
Purchase #7	$198.42	8.481%	$215.248	$215.25	$215.25	$215.20
7 purchase totals =	$928.41		$1,016.2757	$1,016.29	$1,016.30	$1,016.20