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	$96.46	3.758%	$100.085	$100.09	$100.10	$100.10
Purchase #2	$118.94	6.195%	$126.3083	$126.31	$126.30	$126.30
Purchase #3	$40.55	7.772%	$43.7015	$43.70	$43.70	$43.70
Purchase #4	$60.37	7.715%	$65.0275	$65.03	$65.05	$65.00
Purchase #5	$250.56	5.470%	$264.2656	$264.27	$264.25	$264.30
Purchase #6	$99.62	6.155%	$105.7516	$105.75	$105.75	$105.80
Purchase #7	$163.69	4.525%	$171.097	$171.10	$171.10	$171.10
7 purchase totals =	$830.19		$876.2365	$876.25	$876.25	$876.30