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	$159.89	10.375%	$176.4786	$176.48	$176.50	$176.50
Purchase #2	$78.61	6.147%	$83.4422	$83.44	$83.45	$83.40
Purchase #3	$9.45	12.204%	$10.6033	$10.60	$10.60	$10.60
Purchase #4	$79.33	6.713%	$84.6554	$84.66	$84.65	$84.70
Purchase #5	$71.66	9.670%	$78.5895	$78.59	$78.60	$78.60
Purchase #6	$164.74	6.116%	$174.8155	$174.82	$174.80	$174.80
Purchase #7	$111.77	11.512%	$124.637	$124.64	$124.65	$124.60
7 purchase totals =	$675.45		$733.2215	$733.23	$733.25	$733.20