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	$115.43	10.800%	$127.8964	$127.90	$127.90	$127.90
Purchase #2	$219.77	9.626%	$240.9251	$240.93	$240.95	$240.90
Purchase #3	$166.30	8.108%	$179.7836	$179.78	$179.80	$179.80
Purchase #4	$195.75	10.599%	$216.4975	$216.50	$216.50	$216.50
Purchase #5	$101.77	3.502%	$105.334	$105.33	$105.35	$105.30
Purchase #6	$226.35	10.728%	$250.6328	$250.63	$250.65	$250.60
Purchase #7	$19.70	7.645%	$21.2061	$21.21	$21.20	$21.20
7 purchase totals =	$1,045.07		$1,142.2755	$1,142.28	$1,142.35	$1,142.20