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	$174.83	8.723%	$190.0804	$190.08	$190.10	$190.10
Purchase #2	$165.96	13.413%	$188.2202	$188.22	$188.20	$188.20
Purchase #3	$124.26	3.401%	$128.4861	$128.49	$128.50	$128.50
Purchase #4	$133.46	4.324%	$139.2308	$139.23	$139.25	$139.20
Purchase #5	$97.92	12.132%	$109.7997	$109.80	$109.80	$109.80
Purchase #6	$17.83	12.613%	$20.0789	$20.08	$20.10	$20.10
Purchase #7	$9.53	7.265%	$10.2224	$10.22	$10.20	$10.20
7 purchase totals =	$723.79		$786.1185	$786.12	$786.15	$786.10