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	$17.25	11.551%	$19.2425	$19.24	$19.25	$19.20
Purchase #2	$174.31	4.861%	$182.7832	$182.78	$182.80	$182.80
Purchase #3	$19.26	11.176%	$21.4125	$21.41	$21.40	$21.40
Purchase #4	$244.43	3.557%	$253.1244	$253.12	$253.10	$253.10
Purchase #5	$216.39	11.462%	$241.1926	$241.19	$241.20	$241.20
Purchase #6	$47.51	13.215%	$53.7884	$53.79	$53.80	$53.80
Purchase #7	$93.57	6.215%	$99.3854	$99.39	$99.40	$99.40
7 purchase totals =	$812.72		$870.9290	$870.92	$870.95	$870.90