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	$193.68	10.633%	$214.274	$214.27	$214.25	$214.30
Purchase #2	$97.44	13.446%	$110.5418	$110.54	$110.55	$110.50
Purchase #3	$124.82	10.132%	$137.4668	$137.47	$137.45	$137.50
Purchase #4	$85.86	5.447%	$90.5368	$90.54	$90.55	$90.50
Purchase #5	$47.67	13.223%	$53.9734	$53.97	$53.95	$54.00
Purchase #6	$24.60	10.608%	$27.2096	$27.21	$27.20	$27.20
Purchase #7	$90.25	6.865%	$96.4457	$96.45	$96.45	$96.40
7 purchase totals =	$664.32		$730.4481	$730.45	$730.40	$730.40