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	$31.46	13.443%	$35.6892	$35.69	$35.70	$35.70
Purchase #2	$156.78	6.752%	$167.3658	$167.37	$167.35	$167.40
Purchase #3	$90.32	5.274%	$95.0835	$95.08	$95.10	$95.10
Purchase #4	$62.73	7.359%	$67.3463	$67.35	$67.35	$67.30
Purchase #5	$114.92	11.222%	$127.8163	$127.82	$127.80	$127.80
Purchase #6	$40.57	6.596%	$43.246	$43.25	$43.25	$43.20
Purchase #7	$29.34	12.348%	$32.9629	$32.96	$32.95	$33.00
7 purchase totals =	$526.12		$569.5100	$569.52	$569.50	$569.50