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	$124.39	10.275%	$137.1711	$137.17	$137.15	$137.20
Purchase #2	$207.90	10.673%	$230.0892	$230.09	$230.10	$230.10
Purchase #3	$67.92	7.394%	$72.942	$72.94	$72.95	$72.90
Purchase #4	$9.33	7.477%	$10.0276	$10.03	$10.05	$10.00
Purchase #5	$42.84	6.472%	$45.6126	$45.61	$45.60	$45.60
Purchase #6	$110.99	7.515%	$119.3309	$119.33	$119.35	$119.30
Purchase #7	$102.53	6.405%	$109.097	$109.10	$109.10	$109.10
7 purchase totals =	$665.90		$724.2704	$724.27	$724.30	$724.20