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	$126.72	11.693%	$141.5374	$141.54	$141.55	$141.50
Purchase #2	$237.51	6.839%	$253.7533	$253.75	$253.75	$253.80
Purchase #3	$112.33	13.620%	$127.6293	$127.63	$127.65	$127.60
Purchase #4	$196.62	6.865%	$210.118	$210.12	$210.10	$210.10
Purchase #5	$215.80	7.320%	$231.5966	$231.60	$231.60	$231.60
Purchase #6	$91.98	13.352%	$104.2612	$104.26	$104.25	$104.30
Purchase #7	$10.81	11.280%	$12.0294	$12.03	$12.05	$12.00
7 purchase totals =	$991.77		$1,080.9252	$1,080.93	$1,080.95	$1,080.90