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	$107.44	10.406%	$118.6202	$118.62	$118.60	$118.60
Purchase #2	$196.80	10.204%	$216.8815	$216.88	$216.90	$216.90
Purchase #3	$147.46	5.277%	$155.2415	$155.24	$155.25	$155.20
Purchase #4	$35.90	3.415%	$37.126	$37.13	$37.15	$37.10
Purchase #5	$118.27	11.711%	$132.1206	$132.12	$132.10	$132.10
Purchase #6	$90.97	9.460%	$99.5758	$99.58	$99.60	$99.60
Purchase #7	$12.43	13.369%	$14.0918	$14.09	$14.10	$14.10
7 purchase totals =	$709.27		$773.6574	$773.66	$773.70	$773.60