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	$137.71	11.751%	$153.8923	$153.89	$153.90	$153.90
Purchase #2	$243.84	6.567%	$259.853	$259.85	$259.85	$259.90
Purchase #3	$19.39	10.413%	$21.4091	$21.41	$21.40	$21.40
Purchase #4	$109.83	3.858%	$114.0672	$114.07	$114.05	$114.10
Purchase #5	$180.55	13.580%	$205.0687	$205.07	$205.05	$205.10
Purchase #6	$177.56	6.403%	$188.9292	$188.93	$188.95	$188.90
Purchase #7	$95.91	10.300%	$105.7887	$105.79	$105.80	$105.80
7 purchase totals =	$964.79		$1,049.0082	$1,049.01	$1,049.00	$1,049.10