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	$168.25	8.241%	$182.1155	$182.12	$182.10	$182.10
Purchase #2	$79.83	4.528%	$83.4447	$83.44	$83.45	$83.40
Purchase #3	$147.54	9.807%	$162.0092	$162.01	$162.00	$162.00
Purchase #4	$143.32	8.817%	$155.9565	$155.96	$155.95	$156.00
Purchase #5	$144.57	12.137%	$162.1165	$162.12	$162.10	$162.10
Purchase #6	$196.81	6.333%	$209.274	$209.27	$209.25	$209.30
Purchase #7	$84.66	8.189%	$91.5928	$91.59	$91.60	$91.60
7 purchase totals =	$964.98		$1,046.5092	$1,046.51	$1,046.45	$1,046.50