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	$221.87	10.217%	$244.5385	$244.54	$244.55	$244.50
Purchase #2	$240.88	13.533%	$273.4783	$273.48	$273.50	$273.50
Purchase #3	$235.68	5.529%	$248.7107	$248.71	$248.70	$248.70
Purchase #4	$111.52	10.618%	$123.3612	$123.36	$123.35	$123.40
Purchase #5	$32.61	11.276%	$36.2871	$36.29	$36.30	$36.30
Purchase #6	$172.82	13.565%	$196.263	$196.26	$196.25	$196.30
Purchase #7	$203.68	5.612%	$215.1105	$215.11	$215.10	$215.10
7 purchase totals =	$1,219.06		$1,337.7493	$1,337.75	$1,337.75	$1,337.80