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	$145.65	8.517%	$158.055	$158.06	$158.05	$158.10
Purchase #2	$190.35	11.495%	$212.2307	$212.23	$212.25	$212.20
Purchase #3	$57.96	3.380%	$59.919	$59.92	$59.90	$59.90
Purchase #4	$31.90	13.714%	$36.2748	$36.27	$36.25	$36.30
Purchase #5	$89.27	13.755%	$101.5491	$101.55	$101.55	$101.50
Purchase #6	$25.49	9.283%	$27.8562	$27.86	$27.85	$27.90
Purchase #7	$244.63	9.791%	$268.5817	$268.58	$268.60	$268.60
7 purchase totals =	$785.25		$864.4665	$864.47	$864.45	$864.50