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	$47.90	10.333%	$52.8495	$52.85	$52.85	$52.80
Purchase #2	$70.53	8.507%	$76.53	$76.53	$76.55	$76.50
Purchase #3	$83.82	8.470%	$90.9196	$90.92	$90.90	$90.90
Purchase #4	$21.58	12.531%	$24.2842	$24.28	$24.30	$24.30
Purchase #5	$49.68	7.404%	$53.3583	$53.36	$53.35	$53.40
Purchase #6	$247.69	8.191%	$267.9783	$267.98	$268.00	$268.00
Purchase #7	$77.29	8.538%	$83.889	$83.89	$83.90	$83.90
7 purchase totals =	$598.49		$649.8089	$649.81	$649.85	$649.80