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	$56.76	12.510%	$63.8607	$63.86	$63.85	$63.90
Purchase #2	$6.74	5.613%	$7.1183	$7.12	$7.10	$7.10
Purchase #3	$144.30	4.426%	$150.6867	$150.69	$150.70	$150.70
Purchase #4	$45.73	9.582%	$50.1118	$50.11	$50.10	$50.10
Purchase #5	$32.94	7.382%	$35.3716	$35.37	$35.35	$35.40
Purchase #6	$170.84	8.588%	$185.5117	$185.51	$185.50	$185.50
Purchase #7	$116.51	5.792%	$123.2583	$123.26	$123.25	$123.30
7 purchase totals =	$573.82		$615.9191	$615.92	$615.85	$616.00