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	$201.93	8.743%	$219.5847	$219.58	$219.60	$219.60
Purchase #2	$45.46	3.411%	$47.0106	$47.01	$47.00	$47.00
Purchase #3	$138.82	10.307%	$153.1282	$153.13	$153.15	$153.10
Purchase #4	$131.96	5.356%	$139.0278	$139.03	$139.05	$139.00
Purchase #5	$112.41	13.303%	$127.3639	$127.36	$127.35	$127.40
Purchase #6	$61.33	6.641%	$65.4029	$65.40	$65.40	$65.40
Purchase #7	$99.31	4.780%	$104.057	$104.06	$104.05	$104.10
7 purchase totals =	$791.22		$855.5751	$855.57	$855.60	$855.60