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	$162.75	9.440%	$178.1136	$178.11	$178.10	$178.10
Purchase #2	$149.63	8.699%	$162.6463	$162.65	$162.65	$162.60
Purchase #3	$207.43	8.746%	$225.5718	$225.57	$225.55	$225.60
Purchase #4	$38.33	10.832%	$42.4819	$42.48	$42.50	$42.50
Purchase #5	$33.96	11.553%	$37.8834	$37.88	$37.90	$37.90
Purchase #6	$154.61	7.421%	$166.0836	$166.08	$166.10	$166.10
Purchase #7	$234.36	9.127%	$255.75	$255.75	$255.75	$255.80
7 purchase totals =	$981.07		$1,068.5306	$1,068.52	$1,068.55	$1,068.60