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	$59.34	6.102%	$62.9609	$62.96	$62.95	$63.00
Purchase #2	$135.31	7.435%	$145.3703	$145.37	$145.35	$145.40
Purchase #3	$83.37	3.109%	$85.962	$85.96	$85.95	$86.00
Purchase #4	$234.55	13.155%	$265.4051	$265.41	$265.40	$265.40
Purchase #5	$98.88	13.111%	$111.8442	$111.84	$111.85	$111.80
Purchase #6	$224.48	13.385%	$254.5266	$254.53	$254.55	$254.50
Purchase #7	$64.87	7.201%	$69.5413	$69.54	$69.55	$69.50
7 purchase totals =	$900.80		$995.6104	$995.61	$995.60	$995.60