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	$211.71	5.710%	$223.7986	$223.80	$223.80	$223.80
Purchase #2	$171.53	12.397%	$192.7946	$192.79	$192.80	$192.80
Purchase #3	$80.69	11.627%	$90.0718	$90.07	$90.05	$90.10
Purchase #4	$181.27	7.282%	$194.4701	$194.47	$194.45	$194.50
Purchase #5	$233.54	12.450%	$262.6157	$262.62	$262.60	$262.60
Purchase #6	$54.48	10.834%	$60.3824	$60.38	$60.40	$60.40
Purchase #7	$93.25	10.122%	$102.6888	$102.69	$102.70	$102.70
7 purchase totals =	$1,026.47		$1,126.8220	$1,126.82	$1,126.80	$1,126.90