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	$106.49	11.318%	$118.5425	$118.54	$118.55	$118.50
Purchase #2	$91.32	7.824%	$98.4649	$98.46	$98.45	$98.50
Purchase #3	$169.42	6.842%	$181.0117	$181.01	$181.00	$181.00
Purchase #4	$103.95	7.634%	$111.8855	$111.89	$111.90	$111.90
Purchase #5	$83.44	3.870%	$86.6691	$86.67	$86.65	$86.70
Purchase #6	$80.80	3.136%	$83.3339	$83.33	$83.35	$83.30
Purchase #7	$84.27	9.639%	$92.3928	$92.39	$92.40	$92.40
7 purchase totals =	$719.69		$772.3004	$772.29	$772.30	$772.30