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	$86.57	4.823%	$90.7453	$90.75	$90.75	$90.70
Purchase #2	$42.83	6.430%	$45.584	$45.58	$45.60	$45.60
Purchase #3	$51.90	12.385%	$58.3278	$58.33	$58.35	$58.30
Purchase #4	$131.94	7.567%	$141.9239	$141.92	$141.90	$141.90
Purchase #5	$206.84	10.349%	$228.2459	$228.25	$228.25	$228.20
Purchase #6	$30.87	7.448%	$33.1692	$33.17	$33.15	$33.20
Purchase #7	$176.98	5.596%	$186.8838	$186.88	$186.90	$186.90
7 purchase totals =	$727.93		$784.8799	$784.88	$784.90	$784.80