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	$200.28	13.604%	$227.5261	$227.53	$227.55	$227.50
Purchase #2	$56.55	3.405%	$58.4755	$58.48	$58.50	$58.50
Purchase #3	$31.81	3.206%	$32.8298	$32.83	$32.85	$32.80
Purchase #4	$145.39	7.133%	$155.7607	$155.76	$155.75	$155.80
Purchase #5	$229.55	9.728%	$251.8806	$251.88	$251.90	$251.90
Purchase #6	$97.65	3.665%	$101.2289	$101.23	$101.25	$101.20
Purchase #7	$238.69	13.648%	$271.2664	$271.27	$271.25	$271.30
7 purchase totals =	$999.92		$1,098.9680	$1,098.98	$1,099.05	$1,099.00