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	$73.84	7.338%	$79.2584	$79.26	$79.25	$79.30
Purchase #2	$88.65	13.470%	$100.5912	$100.59	$100.60	$100.60
Purchase #3	$5.93	10.690%	$6.5639	$6.56	$6.55	$6.60
Purchase #4	$241.73	8.393%	$262.0184	$262.02	$262.00	$262.00
Purchase #5	$35.46	6.749%	$37.8532	$37.85	$37.85	$37.90
Purchase #6	$166.73	3.409%	$172.4138	$172.41	$172.40	$172.40
Purchase #7	$232.73	4.134%	$242.3511	$242.35	$242.35	$242.40
7 purchase totals =	$845.07		$901.0500	$901.04	$901.00	$901.20