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	$6.73	5.314%	$7.0876	$7.09	$7.10	$7.10
Purchase #2	$165.73	9.281%	$181.1114	$181.11	$181.10	$181.10
Purchase #3	$190.63	5.121%	$200.3922	$200.39	$200.40	$200.40
Purchase #4	$250.98	8.155%	$271.4474	$271.45	$271.45	$271.40
Purchase #5	$65.84	8.578%	$71.4878	$71.49	$71.50	$71.50
Purchase #6	$212.78	7.304%	$228.3215	$228.32	$228.30	$228.30
Purchase #7	$48.64	6.857%	$51.9752	$51.98	$52.00	$52.00
7 purchase totals =	$941.33		$1,011.8231	$1,011.83	$1,011.85	$1,011.80