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	$35.87	4.439%	$37.4623	$37.46	$37.45	$37.50
Purchase #2	$158.87	3.302%	$164.1159	$164.12	$164.10	$164.10
Purchase #3	$238.72	6.822%	$255.0055	$255.01	$255.00	$255.00
Purchase #4	$237.87	3.279%	$245.6698	$245.67	$245.65	$245.70
Purchase #5	$200.81	12.203%	$225.3148	$225.31	$225.30	$225.30
Purchase #6	$207.92	12.268%	$233.4276	$233.43	$233.45	$233.40
Purchase #7	$219.59	11.140%	$244.0523	$244.05	$244.05	$244.10
7 purchase totals =	$1,299.65		$1,405.0482	$1,405.05	$1,405.00	$1,405.10