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	$168.66	3.374%	$174.3506	$174.35	$174.35	$174.40
Purchase #2	$92.86	5.600%	$98.0602	$98.06	$98.05	$98.10
Purchase #3	$235.85	8.578%	$256.0812	$256.08	$256.10	$256.10
Purchase #4	$246.46	6.415%	$262.2704	$262.27	$262.25	$262.30
Purchase #5	$222.94	7.153%	$238.8869	$238.89	$238.90	$238.90
Purchase #6	$213.66	12.703%	$240.8012	$240.80	$240.80	$240.80
Purchase #7	$65.37	3.141%	$67.4233	$67.42	$67.40	$67.40
7 purchase totals =	$1,245.80		$1,337.8738	$1,337.87	$1,337.85	$1,338.00