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	$93.76	7.218%	$100.5276	$100.53	$100.55	$100.50
Purchase #2	$238.30	11.596%	$265.9333	$265.93	$265.95	$265.90
Purchase #3	$243.90	4.806%	$255.6218	$255.62	$255.60	$255.60
Purchase #4	$89.25	7.528%	$95.9687	$95.97	$95.95	$96.00
Purchase #5	$140.32	7.818%	$151.2902	$151.29	$151.30	$151.30
Purchase #6	$125.71	4.518%	$131.3896	$131.39	$131.40	$131.40
Purchase #7	$198.92	4.503%	$207.8774	$207.88	$207.90	$207.90
7 purchase totals =	$1,130.16		$1,208.6086	$1,208.61	$1,208.65	$1,208.60