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	$141.75	10.109%	$156.0795	$156.08	$156.10	$156.10
Purchase #2	$90.30	12.550%	$101.6327	$101.63	$101.65	$101.60
Purchase #3	$174.38	12.638%	$196.4181	$196.42	$196.40	$196.40
Purchase #4	$69.49	3.763%	$72.1049	$72.10	$72.10	$72.10
Purchase #5	$152.98	3.828%	$158.8361	$158.84	$158.85	$158.80
Purchase #6	$51.51	12.133%	$57.7597	$57.76	$57.75	$57.80
Purchase #7	$204.92	6.711%	$218.6722	$218.67	$218.65	$218.70
7 purchase totals =	$885.33		$961.5032	$961.50	$961.50	$961.50