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	$150.41	10.440%	$166.1128	$166.11	$166.10	$166.10
Purchase #2	$90.80	8.504%	$98.5216	$98.52	$98.50	$98.50
Purchase #3	$116.48	8.452%	$126.3249	$126.32	$126.30	$126.30
Purchase #4	$132.77	8.663%	$144.2719	$144.27	$144.25	$144.30
Purchase #5	$224.45	4.816%	$235.2595	$235.26	$235.25	$235.30
Purchase #6	$86.45	5.237%	$90.9774	$90.98	$91.00	$91.00
Purchase #7	$58.50	6.868%	$62.5178	$62.52	$62.50	$62.50
7 purchase totals =	$859.86		$923.9859	$923.98	$923.90	$924.00