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	$46.78	3.279%	$48.3139	$48.31	$48.30	$48.30
Purchase #2	$140.65	8.491%	$152.5926	$152.59	$152.60	$152.60
Purchase #3	$73.64	6.424%	$78.3706	$78.37	$78.35	$78.40
Purchase #4	$50.98	5.372%	$53.7186	$53.72	$53.70	$53.70
Purchase #5	$208.96	5.592%	$220.645	$220.65	$220.65	$220.60
Purchase #6	$156.35	9.711%	$171.5331	$171.53	$171.55	$171.50
Purchase #7	$170.88	7.279%	$183.3184	$183.32	$183.30	$183.30
7 purchase totals =	$848.24		$908.4922	$908.49	$908.45	$908.40