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	$105.35	7.381%	$113.1259	$113.13	$113.15	$113.10
Purchase #2	$187.75	4.604%	$196.394	$196.39	$196.40	$196.40
Purchase #3	$186.81	12.681%	$210.4994	$210.50	$210.50	$210.50
Purchase #4	$67.82	5.545%	$71.5806	$71.58	$71.60	$71.60
Purchase #5	$182.33	3.267%	$188.2867	$188.29	$188.30	$188.30
Purchase #6	$165.71	9.711%	$181.8021	$181.80	$181.80	$181.80
Purchase #7	$30.28	12.285%	$33.9999	$34.00	$34.00	$34.00
7 purchase totals =	$926.05		$995.6886	$995.69	$995.75	$995.70