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	$131.96	11.815%	$147.5511	$147.55	$147.55	$147.60
Purchase #2	$73.83	6.462%	$78.6009	$78.60	$78.60	$78.60
Purchase #3	$233.97	13.821%	$266.307	$266.31	$266.30	$266.30
Purchase #4	$9.28	7.247%	$9.9525	$9.95	$9.95	$10.00
Purchase #5	$99.31	8.846%	$108.095	$108.10	$108.10	$108.10
Purchase #6	$50.97	4.586%	$53.3075	$53.31	$53.30	$53.30
Purchase #7	$177.27	10.654%	$196.1563	$196.16	$196.15	$196.20
7 purchase totals =	$776.59		$859.9703	$859.98	$859.95	$860.10