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	$94.94	12.678%	$106.9765	$106.98	$107.00	$107.00
Purchase #2	$100.65	10.665%	$111.3843	$111.38	$111.40	$111.40
Purchase #3	$89.82	9.831%	$98.6502	$98.65	$98.65	$98.70
Purchase #4	$96.26	10.762%	$106.6195	$106.62	$106.60	$106.60
Purchase #5	$148.69	3.191%	$153.4347	$153.43	$153.45	$153.40
Purchase #6	$142.52	9.656%	$156.2817	$156.28	$156.30	$156.30
Purchase #7	$217.47	10.821%	$241.0024	$241.00	$241.00	$241.00
7 purchase totals =	$890.35		$974.3493	$974.34	$974.40	$974.40