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	$158.84	5.175%	$167.06	$167.06	$167.05	$167.10
Purchase #2	$183.78	10.542%	$203.1541	$203.15	$203.15	$203.20
Purchase #3	$249.71	3.457%	$258.3425	$258.34	$258.35	$258.30
Purchase #4	$91.29	9.117%	$99.6129	$99.61	$99.60	$99.60
Purchase #5	$28.85	9.540%	$31.6023	$31.60	$31.60	$31.60
Purchase #6	$224.62	5.243%	$236.3968	$236.40	$236.40	$236.40
Purchase #7	$120.28	9.247%	$131.4023	$131.40	$131.40	$131.40
7 purchase totals =	$1,057.37		$1,127.5709	$1,127.56	$1,127.55	$1,127.60