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	$167.62	12.448%	$188.4853	$188.49	$188.50	$188.50
Purchase #2	$57.29	10.329%	$63.2075	$63.21	$63.20	$63.20
Purchase #3	$85.35	5.797%	$90.2977	$90.30	$90.30	$90.30
Purchase #4	$128.91	12.613%	$145.1694	$145.17	$145.15	$145.20
Purchase #5	$120.61	13.712%	$137.148	$137.15	$137.15	$137.10
Purchase #6	$239.53	11.111%	$266.1442	$266.14	$266.15	$266.10
Purchase #7	$160.59	13.690%	$182.5748	$182.57	$182.55	$182.60
7 purchase totals =	$959.90		$1,073.0269	$1,073.03	$1,073.00	$1,073.00