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	$189.40	4.861%	$198.6067	$198.61	$198.60	$198.60
Purchase #2	$188.82	5.854%	$199.8735	$199.87	$199.85	$199.90
Purchase #3	$57.36	6.712%	$61.21	$61.21	$61.20	$61.20
Purchase #4	$157.80	3.144%	$162.7612	$162.76	$162.75	$162.80
Purchase #5	$68.88	13.405%	$78.1134	$78.11	$78.10	$78.10
Purchase #6	$226.86	10.146%	$249.8772	$249.88	$249.90	$249.90
Purchase #7	$11.74	5.590%	$12.3963	$12.40	$12.40	$12.40
7 purchase totals =	$900.86		$962.8383	$962.84	$962.80	$962.90