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	$187.58	13.271%	$212.4737	$212.47	$212.45	$212.50
Purchase #2	$40.42	8.723%	$43.9458	$43.95	$43.95	$43.90
Purchase #3	$226.33	5.533%	$238.8528	$238.85	$238.85	$238.90
Purchase #4	$157.41	9.411%	$172.2239	$172.22	$172.20	$172.20
Purchase #5	$102.76	3.496%	$106.3525	$106.35	$106.35	$106.40
Purchase #6	$89.85	7.671%	$96.7424	$96.74	$96.75	$96.70
Purchase #7	$175.85	7.658%	$189.3166	$189.32	$189.30	$189.30
7 purchase totals =	$980.20		$1,059.9077	$1,059.90	$1,059.85	$1,059.90