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	$131.57	10.567%	$145.473	$145.47	$145.45	$145.50
Purchase #2	$130.63	10.511%	$144.3605	$144.36	$144.35	$144.40
Purchase #3	$167.66	13.488%	$190.274	$190.27	$190.25	$190.30
Purchase #4	$31.92	10.667%	$35.3249	$35.32	$35.30	$35.30
Purchase #5	$37.53	6.409%	$39.9353	$39.94	$39.95	$39.90
Purchase #6	$57.43	8.782%	$62.4735	$62.47	$62.45	$62.50
Purchase #7	$243.99	8.154%	$263.8849	$263.88	$263.90	$263.90
7 purchase totals =	$800.73		$881.7261	$881.71	$881.65	$881.80