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	$190.75	3.203%	$196.8597	$196.86	$196.85	$196.90
Purchase #2	$204.68	7.561%	$220.1559	$220.16	$220.15	$220.20
Purchase #3	$172.94	7.781%	$186.3965	$186.40	$186.40	$186.40
Purchase #4	$70.45	8.323%	$76.3136	$76.31	$76.30	$76.30
Purchase #5	$38.50	5.254%	$40.5228	$40.52	$40.50	$40.50
Purchase #6	$5.72	9.483%	$6.2624	$6.26	$6.25	$6.30
Purchase #7	$153.29	12.799%	$172.9096	$172.91	$172.90	$172.90
7 purchase totals =	$836.33		$899.4205	$899.42	$899.35	$899.50