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	$94.55	11.303%	$105.237	$105.24	$105.25	$105.20
Purchase #2	$112.75	11.803%	$126.0579	$126.06	$126.05	$126.10
Purchase #3	$88.90	4.453%	$92.8587	$92.86	$92.85	$92.90
Purchase #4	$138.76	9.635%	$152.1295	$152.13	$152.15	$152.10
Purchase #5	$110.41	5.416%	$116.3898	$116.39	$116.40	$116.40
Purchase #6	$106.42	12.836%	$120.0801	$120.08	$120.10	$120.10
Purchase #7	$82.83	9.354%	$90.5779	$90.58	$90.60	$90.60
7 purchase totals =	$734.62		$803.3309	$803.34	$803.40	$803.40