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	$118.32	8.720%	$128.6375	$128.64	$128.65	$128.60
Purchase #2	$250.89	11.779%	$280.4423	$280.44	$280.45	$280.40
Purchase #3	$213.49	7.338%	$229.1559	$229.16	$229.15	$229.20
Purchase #4	$46.27	13.357%	$52.4503	$52.45	$52.45	$52.50
Purchase #5	$223.33	5.809%	$236.3032	$236.30	$236.30	$236.30
Purchase #6	$174.27	8.533%	$189.1405	$189.14	$189.15	$189.10
Purchase #7	$97.73	7.725%	$105.2796	$105.28	$105.30	$105.30
7 purchase totals =	$1,124.30		$1,221.4093	$1,221.41	$1,221.45	$1,221.40