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	$93.54	6.622%	$99.7342	$99.73	$99.75	$99.70
Purchase #2	$166.45	3.838%	$172.8384	$172.84	$172.85	$172.80
Purchase #3	$60.29	11.274%	$67.0871	$67.09	$67.10	$67.10
Purchase #4	$115.67	12.467%	$130.0906	$130.09	$130.10	$130.10
Purchase #5	$92.31	3.309%	$95.3645	$95.36	$95.35	$95.40
Purchase #6	$56.45	4.648%	$59.0738	$59.07	$59.05	$59.10
Purchase #7	$114.47	9.658%	$125.5255	$125.53	$125.55	$125.50
7 purchase totals =	$699.18		$749.7141	$749.71	$749.75	$749.70