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	$127.40	11.605%	$142.1848	$142.18	$142.20	$142.20
Purchase #2	$175.70	12.841%	$198.2616	$198.26	$198.25	$198.30
Purchase #3	$86.99	4.216%	$90.6575	$90.66	$90.65	$90.70
Purchase #4	$73.26	12.595%	$82.4871	$82.49	$82.50	$82.50
Purchase #5	$147.78	8.617%	$160.5142	$160.51	$160.50	$160.50
Purchase #6	$56.46	11.575%	$62.9952	$63.00	$63.00	$63.00
Purchase #7	$98.95	12.865%	$111.6799	$111.68	$111.70	$111.70
7 purchase totals =	$766.54		$848.7803	$848.78	$848.80	$848.90