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	$62.73	13.149%	$70.9784	$70.98	$71.00	$71.00
Purchase #2	$57.76	7.104%	$61.8633	$61.86	$61.85	$61.90
Purchase #3	$131.38	4.266%	$136.9847	$136.98	$137.00	$137.00
Purchase #4	$131.67	10.517%	$145.5177	$145.52	$145.50	$145.50
Purchase #5	$200.36	10.363%	$221.1233	$221.12	$221.10	$221.10
Purchase #6	$169.82	7.684%	$182.869	$182.87	$182.85	$182.90
Purchase #7	$157.39	6.308%	$167.3182	$167.32	$167.30	$167.30
7 purchase totals =	$911.11		$986.6546	$986.65	$986.60	$986.70