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	$47.86	10.378%	$52.8269	$52.83	$52.85	$52.80
Purchase #2	$76.76	7.352%	$82.4034	$82.40	$82.40	$82.40
Purchase #3	$98.80	12.219%	$110.8724	$110.87	$110.85	$110.90
Purchase #4	$62.99	6.359%	$66.9955	$67.00	$67.00	$67.00
Purchase #5	$99.29	10.578%	$109.7929	$109.79	$109.80	$109.80
Purchase #6	$152.31	7.697%	$164.0333	$164.03	$164.05	$164.00
Purchase #7	$36.87	7.321%	$39.5693	$39.57	$39.55	$39.60
7 purchase totals =	$574.88		$626.4937	$626.49	$626.50	$626.50