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	$167.30	5.223%	$176.0381	$176.04	$176.05	$176.00
Purchase #2	$92.40	9.625%	$101.2935	$101.29	$101.30	$101.30
Purchase #3	$78.98	4.332%	$82.4014	$82.40	$82.40	$82.40
Purchase #4	$185.50	11.552%	$206.929	$206.93	$206.95	$206.90
Purchase #5	$57.90	8.500%	$62.8215	$62.82	$62.80	$62.80
Purchase #6	$34.89	7.533%	$37.5183	$37.52	$37.50	$37.50
Purchase #7	$107.31	10.479%	$118.555	$118.56	$118.55	$118.60
7 purchase totals =	$724.28		$785.5568	$785.56	$785.55	$785.50