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	$195.43	8.755%	$212.5399	$212.54	$212.55	$212.50
Purchase #2	$157.41	3.248%	$162.5227	$162.52	$162.50	$162.50
Purchase #3	$92.90	5.402%	$97.9185	$97.92	$97.90	$97.90
Purchase #4	$16.92	11.797%	$18.9161	$18.92	$18.90	$18.90
Purchase #5	$249.74	6.654%	$266.3577	$266.36	$266.35	$266.40
Purchase #6	$128.38	11.305%	$142.8934	$142.89	$142.90	$142.90
Purchase #7	$54.50	12.267%	$61.1855	$61.19	$61.20	$61.20
7 purchase totals =	$895.28		$962.3338	$962.34	$962.30	$962.30