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	$180.62	13.720%	$205.4011	$205.40	$205.40	$205.40
Purchase #2	$7.59	13.514%	$8.6157	$8.62	$8.60	$8.60
Purchase #3	$125.57	13.229%	$142.1817	$142.18	$142.20	$142.20
Purchase #4	$25.73	7.297%	$27.6075	$27.61	$27.60	$27.60
Purchase #5	$92.34	11.383%	$102.8511	$102.85	$102.85	$102.90
Purchase #6	$191.50	4.634%	$200.3741	$200.37	$200.35	$200.40
Purchase #7	$163.37	13.323%	$185.1358	$185.14	$185.15	$185.10
7 purchase totals =	$786.72		$872.1670	$872.17	$872.15	$872.20