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	$47.78	6.195%	$50.74	$50.74	$50.75	$50.70
Purchase #2	$212.70	7.233%	$228.0846	$228.08	$228.10	$228.10
Purchase #3	$208.60	4.442%	$217.866	$217.87	$217.85	$217.90
Purchase #4	$85.38	12.419%	$95.9833	$95.98	$96.00	$96.00
Purchase #5	$192.29	9.541%	$210.6364	$210.64	$210.65	$210.60
Purchase #6	$179.37	3.220%	$185.1457	$185.15	$185.15	$185.10
Purchase #7	$172.47	11.257%	$191.8849	$191.88	$191.90	$191.90
7 purchase totals =	$1,098.59		$1,180.3409	$1,180.34	$1,180.40	$1,180.30