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	$140.40	4.403%	$146.5818	$146.58	$146.60	$146.60
Purchase #2	$183.72	13.758%	$208.9962	$209.00	$209.00	$209.00
Purchase #3	$149.98	10.450%	$165.6529	$165.65	$165.65	$165.70
Purchase #4	$171.37	4.612%	$179.2736	$179.27	$179.25	$179.30
Purchase #5	$150.91	3.426%	$156.0802	$156.08	$156.10	$156.10
Purchase #6	$228.90	5.555%	$241.6154	$241.62	$241.60	$241.60
Purchase #7	$6.78	9.809%	$7.4451	$7.45	$7.45	$7.40
7 purchase totals =	$1,032.06		$1,105.6452	$1,105.65	$1,105.65	$1,105.70