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	$138.38	11.201%	$153.8799	$153.88	$153.90	$153.90
Purchase #2	$225.89	5.764%	$238.9103	$238.91	$238.90	$238.90
Purchase #3	$226.81	3.537%	$234.8323	$234.83	$234.85	$234.80
Purchase #4	$173.48	6.550%	$184.8429	$184.84	$184.85	$184.80
Purchase #5	$86.61	12.379%	$97.3315	$97.33	$97.35	$97.30
Purchase #6	$62.91	7.268%	$67.4823	$67.48	$67.50	$67.50
Purchase #7	$31.98	10.242%	$35.2554	$35.26	$35.25	$35.30
7 purchase totals =	$946.06		$1,012.5346	$1,012.53	$1,012.60	$1,012.50