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	$158.69	13.283%	$179.7688	$179.77	$179.75	$179.80
Purchase #2	$51.94	6.119%	$55.1182	$55.12	$55.10	$55.10
Purchase #3	$13.61	11.115%	$15.1228	$15.12	$15.10	$15.10
Purchase #4	$226.74	10.621%	$250.8221	$250.82	$250.80	$250.80
Purchase #5	$139.40	7.853%	$150.3471	$150.35	$150.35	$150.30
Purchase #6	$119.43	7.470%	$128.3514	$128.35	$128.35	$128.40
Purchase #7	$223.87	7.158%	$239.8946	$239.89	$239.90	$239.90
7 purchase totals =	$933.68		$1,019.4250	$1,019.42	$1,019.35	$1,019.40