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	$42.47	7.736%	$45.7555	$45.76	$45.75	$45.80
Purchase #2	$219.73	10.492%	$242.7841	$242.78	$242.80	$242.80
Purchase #3	$163.32	9.445%	$178.7456	$178.75	$178.75	$178.70
Purchase #4	$197.34	11.288%	$219.6157	$219.62	$219.60	$219.60
Purchase #5	$84.78	8.392%	$91.8947	$91.89	$91.90	$91.90
Purchase #6	$125.66	4.511%	$131.3285	$131.33	$131.35	$131.30
Purchase #7	$105.87	8.493%	$114.8615	$114.86	$114.85	$114.90
7 purchase totals =	$939.17		$1,024.9856	$1,024.99	$1,025.00	$1,025.00