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	$136.56	11.606%	$152.4092	$152.41	$152.40	$152.40
Purchase #2	$238.46	9.668%	$261.5143	$261.51	$261.50	$261.50
Purchase #3	$99.66	3.227%	$102.876	$102.88	$102.90	$102.90
Purchase #4	$198.69	10.676%	$219.9021	$219.90	$219.90	$219.90
Purchase #5	$174.95	7.119%	$187.4047	$187.40	$187.40	$187.40
Purchase #6	$79.43	7.440%	$85.3396	$85.34	$85.35	$85.30
Purchase #7	$127.99	12.568%	$144.0758	$144.08	$144.10	$144.10
7 purchase totals =	$1,055.74		$1,153.5217	$1,153.52	$1,153.55	$1,153.50