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	$248.28	4.729%	$260.0212	$260.02	$260.00	$260.00
Purchase #2	$165.83	11.759%	$185.3299	$185.33	$185.35	$185.30
Purchase #3	$186.88	7.374%	$200.6605	$200.66	$200.65	$200.70
Purchase #4	$14.98	4.133%	$15.5991	$15.60	$15.60	$15.60
Purchase #5	$244.36	4.673%	$255.7789	$255.78	$255.80	$255.80
Purchase #6	$186.57	6.172%	$198.0851	$198.09	$198.10	$198.10
Purchase #7	$40.48	12.539%	$45.5558	$45.56	$45.55	$45.60
7 purchase totals =	$1,087.38		$1,161.0305	$1,161.04	$1,161.05	$1,161.10