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	$50.43	3.718%	$52.305	$52.31	$52.30	$52.30
Purchase #2	$95.44	5.280%	$100.4792	$100.48	$100.50	$100.50
Purchase #3	$173.31	5.487%	$182.8195	$182.82	$182.80	$182.80
Purchase #4	$171.74	4.538%	$179.5336	$179.53	$179.55	$179.50
Purchase #5	$31.63	4.395%	$33.0201	$33.02	$33.00	$33.00
Purchase #6	$6.92	9.730%	$7.5933	$7.59	$7.60	$7.60
Purchase #7	$103.98	7.391%	$111.6652	$111.67	$111.65	$111.70
7 purchase totals =	$633.45		$667.4159	$667.42	$667.40	$667.40