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	$154.25	7.824%	$166.3185	$166.32	$166.30	$166.30
Purchase #2	$89.93	3.251%	$92.8536	$92.85	$92.85	$92.90
Purchase #3	$144.88	13.254%	$164.0824	$164.08	$164.10	$164.10
Purchase #4	$175.59	13.229%	$198.8188	$198.82	$198.80	$198.80
Purchase #5	$107.73	11.724%	$120.3603	$120.36	$120.35	$120.40
Purchase #6	$137.75	10.817%	$152.6504	$152.65	$152.65	$152.70
Purchase #7	$139.28	5.496%	$146.9348	$146.93	$146.95	$146.90
7 purchase totals =	$949.41		$1,042.0188	$1,042.01	$1,042.00	$1,042.10