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	$77.96	10.397%	$86.0655	$86.07	$86.05	$86.10
Purchase #2	$99.69	9.730%	$109.3898	$109.39	$109.40	$109.40
Purchase #3	$147.65	13.332%	$167.3347	$167.33	$167.35	$167.30
Purchase #4	$249.40	3.544%	$258.2387	$258.24	$258.25	$258.20
Purchase #5	$224.97	3.773%	$233.4581	$233.46	$233.45	$233.50
Purchase #6	$185.98	13.598%	$211.2696	$211.27	$211.25	$211.30
Purchase #7	$90.41	4.661%	$94.624	$94.62	$94.60	$94.60
7 purchase totals =	$1,076.06		$1,160.3804	$1,160.38	$1,160.35	$1,160.40