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	$97.66	3.681%	$101.2549	$101.25	$101.25	$101.30
Purchase #2	$80.25	11.441%	$89.4314	$89.43	$89.45	$89.40
Purchase #3	$91.89	10.317%	$101.3703	$101.37	$101.35	$101.40
Purchase #4	$186.89	5.303%	$196.8008	$196.80	$196.80	$196.80
Purchase #5	$151.26	3.162%	$156.0428	$156.04	$156.05	$156.00
Purchase #6	$11.93	13.820%	$13.5787	$13.58	$13.60	$13.60
Purchase #7	$156.53	6.345%	$166.4618	$166.46	$166.45	$166.50
7 purchase totals =	$776.41		$824.9407	$824.93	$824.95	$825.00