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	$230.48	8.706%	$250.5456	$250.55	$250.55	$250.50
Purchase #2	$31.75	11.223%	$35.3133	$35.31	$35.30	$35.30
Purchase #3	$229.59	3.823%	$238.3672	$238.37	$238.35	$238.40
Purchase #4	$11.89	12.556%	$13.3829	$13.38	$13.40	$13.40
Purchase #5	$136.52	8.711%	$148.4123	$148.41	$148.40	$148.40
Purchase #6	$241.40	13.220%	$273.3131	$273.31	$273.30	$273.30
Purchase #7	$136.72	11.671%	$152.6766	$152.68	$152.70	$152.70
7 purchase totals =	$1,018.35		$1,112.0110	$1,112.01	$1,112.00	$1,112.00