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	$52.96	11.632%	$59.1203	$59.12	$59.10	$59.10
Purchase #2	$150.97	13.349%	$171.123	$171.12	$171.10	$171.10
Purchase #3	$163.95	3.604%	$169.8588	$169.86	$169.85	$169.90
Purchase #4	$82.78	7.696%	$89.1507	$89.15	$89.15	$89.20
Purchase #5	$209.58	4.617%	$219.2563	$219.26	$219.25	$219.30
Purchase #6	$159.25	9.744%	$174.7673	$174.77	$174.75	$174.80
Purchase #7	$132.40	4.669%	$138.5818	$138.58	$138.60	$138.60
7 purchase totals =	$951.89		$1,021.8582	$1,021.86	$1,021.80	$1,022.00