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	$166.48	3.117%	$171.6692	$171.67	$171.65	$171.70
Purchase #2	$162.26	13.777%	$184.6146	$184.61	$184.60	$184.60
Purchase #3	$77.85	6.562%	$82.9585	$82.96	$82.95	$83.00
Purchase #4	$126.78	12.725%	$142.9128	$142.91	$142.90	$142.90
Purchase #5	$106.86	11.448%	$119.0933	$119.09	$119.10	$119.10
Purchase #6	$203.58	4.253%	$212.2383	$212.24	$212.25	$212.20
Purchase #7	$92.28	12.197%	$103.5354	$103.54	$103.55	$103.50
7 purchase totals =	$936.09		$1,017.0221	$1,017.02	$1,017.00	$1,017.00