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	$218.42	7.528%	$234.8627	$234.86	$234.85	$234.90
Purchase #2	$174.26	12.491%	$196.0268	$196.03	$196.05	$196.00
Purchase #3	$53.32	3.736%	$55.312	$55.31	$55.30	$55.30
Purchase #4	$224.45	9.172%	$245.0366	$245.04	$245.05	$245.00
Purchase #5	$183.98	6.811%	$196.5109	$196.51	$196.50	$196.50
Purchase #6	$110.94	3.447%	$114.7641	$114.76	$114.75	$114.80
Purchase #7	$165.48	9.286%	$180.8465	$180.85	$180.85	$180.80
7 purchase totals =	$1,130.85		$1,223.3596	$1,223.36	$1,223.35	$1,223.30