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	$117.30	10.793%	$129.9602	$129.96	$129.95	$130.00
Purchase #2	$87.58	4.713%	$91.7076	$91.71	$91.70	$91.70
Purchase #3	$172.84	11.839%	$193.3025	$193.30	$193.30	$193.30
Purchase #4	$164.61	12.796%	$185.6735	$185.67	$185.65	$185.70
Purchase #5	$100.25	5.153%	$105.4159	$105.42	$105.40	$105.40
Purchase #6	$132.61	6.554%	$141.3013	$141.30	$141.30	$141.30
Purchase #7	$157.72	6.809%	$168.4592	$168.46	$168.45	$168.50
7 purchase totals =	$932.91		$1,015.8202	$1,015.82	$1,015.75	$1,015.90