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	$243.84	11.474%	$271.8182	$271.82	$271.80	$271.80
Purchase #2	$89.55	10.102%	$98.5963	$98.60	$98.60	$98.60
Purchase #3	$114.76	11.514%	$127.9735	$127.97	$127.95	$128.00
Purchase #4	$49.50	3.268%	$51.1177	$51.12	$51.10	$51.10
Purchase #5	$70.78	3.738%	$73.4258	$73.43	$73.45	$73.40
Purchase #6	$10.82	6.807%	$11.5565	$11.56	$11.55	$11.60
Purchase #7	$83.97	10.689%	$92.9456	$92.95	$92.95	$92.90
7 purchase totals =	$663.22		$727.4336	$727.45	$727.40	$727.40