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	$87.56	4.685%	$91.6622	$91.66	$91.65	$91.70
Purchase #2	$35.31	10.494%	$39.0154	$39.02	$39.00	$39.00
Purchase #3	$166.37	3.255%	$171.7853	$171.79	$171.80	$171.80
Purchase #4	$75.64	9.358%	$82.7184	$82.72	$82.70	$82.70
Purchase #5	$189.93	9.159%	$207.3257	$207.33	$207.35	$207.30
Purchase #6	$233.43	13.534%	$265.0224	$265.02	$265.00	$265.00
Purchase #7	$178.85	10.107%	$196.9264	$196.93	$196.95	$196.90
7 purchase totals =	$967.09		$1,054.4558	$1,054.47	$1,054.45	$1,054.40