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	$235.86	13.568%	$267.8615	$267.86	$267.85	$267.90
Purchase #2	$51.49	8.535%	$55.8847	$55.88	$55.90	$55.90
Purchase #3	$52.47	4.479%	$54.8201	$54.82	$54.80	$54.80
Purchase #4	$70.72	4.333%	$73.7843	$73.78	$73.80	$73.80
Purchase #5	$240.43	4.615%	$251.5258	$251.53	$251.55	$251.50
Purchase #6	$155.89	7.727%	$167.9356	$167.94	$167.95	$167.90
Purchase #7	$153.35	13.441%	$173.9618	$173.96	$173.95	$174.00
7 purchase totals =	$960.21		$1,045.7738	$1,045.77	$1,045.80	$1,045.80