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	$82.47	10.439%	$91.079	$91.08	$91.10	$91.10
Purchase #2	$116.39	8.142%	$125.8665	$125.87	$125.85	$125.90
Purchase #3	$203.89	7.455%	$219.09	$219.09	$219.10	$219.10
Purchase #4	$205.40	3.222%	$212.018	$212.02	$212.00	$212.00
Purchase #5	$181.26	8.606%	$196.8592	$196.86	$196.85	$196.90
Purchase #6	$133.50	4.232%	$139.1497	$139.15	$139.15	$139.10
Purchase #7	$61.94	9.229%	$67.6564	$67.66	$67.65	$67.70
7 purchase totals =	$984.85		$1,051.7188	$1,051.73	$1,051.70	$1,051.80