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	$99.90	10.650%	$110.5394	$110.54	$110.55	$110.50
Purchase #2	$246.60	3.444%	$255.0929	$255.09	$255.10	$255.10
Purchase #3	$81.71	9.527%	$89.4945	$89.49	$89.50	$89.50
Purchase #4	$93.86	7.236%	$100.6517	$100.65	$100.65	$100.70
Purchase #5	$218.80	13.474%	$248.2811	$248.28	$248.30	$248.30
Purchase #6	$140.60	4.532%	$146.972	$146.97	$146.95	$147.00
Purchase #7	$183.50	4.324%	$191.4345	$191.43	$191.45	$191.40
7 purchase totals =	$1,064.97		$1,142.4661	$1,142.45	$1,142.50	$1,142.50