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	$16.94	12.278%	$19.0199	$19.02	$19.00	$19.00
Purchase #2	$99.34	12.848%	$112.1032	$112.10	$112.10	$112.10
Purchase #3	$176.84	10.238%	$194.9449	$194.94	$194.95	$194.90
Purchase #4	$89.31	7.281%	$95.8127	$95.81	$95.80	$95.80
Purchase #5	$74.78	4.690%	$78.2872	$78.29	$78.30	$78.30
Purchase #6	$20.32	9.840%	$22.3195	$22.32	$22.30	$22.30
Purchase #7	$72.41	4.800%	$75.8857	$75.89	$75.90	$75.90
7 purchase totals =	$549.94		$598.3731	$598.37	$598.35	$598.30