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	$97.63	12.320%	$109.658	$109.66	$109.65	$109.70
Purchase #2	$167.57	4.711%	$175.4642	$175.46	$175.45	$175.50
Purchase #3	$219.65	13.627%	$249.5817	$249.58	$249.60	$249.60
Purchase #4	$102.27	13.739%	$116.3209	$116.32	$116.30	$116.30
Purchase #5	$85.98	9.331%	$94.0028	$94.00	$94.00	$94.00
Purchase #6	$166.52	5.354%	$175.4355	$175.44	$175.45	$175.40
Purchase #7	$147.71	12.558%	$166.2594	$166.26	$166.25	$166.30
7 purchase totals =	$987.33		$1,086.7225	$1,086.72	$1,086.70	$1,086.80